THE CONCRETE MAGAZINE SPRING 2019 www.aspirebridge.org

Gerald Desmond Bridge Long Beach,

MARYLAND ROUTE 195 (CARROLL AVENUE) BRIDGE OVER SLIGO CREEK Tacoma Park, Maryland

NORTHWEST CORRIDOR EXPRESS LANES Marietta, Georgia

BROTHERHOOD BRIDGE (MENDENHALL RIVER BRIDGE)

Juneau, Alaska Permit No. 567 No. Permit

Lebanon Junction, KY Junction, Lebanon SARAH MILDRED LONG BRIDGE Postage Paid Postage Presorted Standard Presorted Portsmouth, New Hampshire, and Kittery, Maine

CONTENTS 6 Features Changing Perceptions 6 DYWIDAG-Systems International’s new high-tech inspection and monitoring tools add to its selection of post-tensioning products and services, enhancing its role as a specialty contractor. Carroll Avenue Bridge Over Sligo Creek 12 Northwest Corridor Express Lanes 16 Brotherhood Bridge Over the Mendenhall River 20 Sarah Mildred Long Bridge 24

Photo: DSI. Departments Editorial 2 12 Concrete Calendar 4 Perspective—Quantitative Assessment of Resilience and Sustainability 10 Aesthetics Commentary 27 Concrete Bridge Technology—Observations from 30 Years of Inspecting Post-Tensioned Structures 28 Concrete Bridge Technology—Seismic Behavior of Reinforced-Concrete-Filled Steel Tubes 32 Concrete Bridge Technology—Sarah Mildred Long Bridge Tower Foundation Construction 34

Photo: Johnson, Mirmiran & Thompson. Concrete Bridge Technology—Implementation of an Electrically Isolated Tendon Post-Tensioning System in the United States 36 24 Concrete Bridge Technology—Sweep in Precast, Bridge Girders 38 Safety and Serviceability— Managing Structures Affected by Delayed Ettringite Formation and Alkali-Silica Reaction 42 FHWA—Advancing Bridge Repair and Preservation Using Ultra-High-Performance Concrete 45 State—Alabama 47 LRFD—AASHTO LRFD Bridge Design Specifications: Service IV Load Combination 51

This issue’s Concrete Connections will DSI. Photo: appear online at aspirebridge.org. Photo: Maine Department of Transportation. Advertisers’ Index DYWIDAG-Systems Max USA Corp ...... 44 Poseidon Barge Ltd ...... 11 International USA Inc...... 5 Mi-Jack Products Inc ... Inside Back Cover Stalite ...... 31 FIGG ...... Inside Front Cover PERI ...... Back Cover Williams Form ...... 52 HDR Inc...... 3 PCI ...... 15, 27, 45, 50

ASPIRE Spring 2019 | 1 EDITORIAL

Editor-in-Chief Vehicular Trends and the Future of William N. Nickas • [email protected] Managing Technical Editor Designing for versatility will be key as technology improves life Dr. Reid W. Castrodale Technical Editor Dr. Krista M. Brown

Photo: PCI. William N. Nickas, Editor-in-Chief Program Manager Nancy Turner • [email protected] s members of the bridge engineering profession, example, the slab tracks originally designed for buses A we want our structures to have a service life of might be adapted for elevated, personal autonomous Associate Editor 75–100 years or even longer. None of us wants to see a vehicle pods. If that happens, we will need to formulate Emily B. Lorenz • [email protected] 20-year-old bridge removed for structural or operational operational protocols, such as how to manage a Copy Editor reasons. But, if we are to build long-lasting bridges, we disabled autonomous vehicle on a confined corridor. Elizabeth Nishiura need to anticipate the vehicular trends of the future. My Will connected trucks operate in the corridors and on Layout Design curiosity about those trends was sparked earlier this year structures? That innovation could have implications Walt Furie when I attended the Transportation Research Board’s for the strength requirements of the structures or the annual meeting, where participants could observe and weight limit of the individual trucks. Editorial Advisory Board ride the Federal Highway Administration’s autonomous An area of uncertainty is throughput in our future William N. Nickas, Precast/Prestressed vehicle. I then attended a chapter meeting of the traffic systems. I have heard it might increase, but it Concrete Institute International Bridge, Tunnel and Turnpike Association, could decrease if computer-controlled autonomous Dr. Reid W. Castrodale, Castrodale where I was eager to learn what financial professionals vehicles require increased headways to reduce the risk Engineering Consultants PC and transportation planners envision for the future of for collisions. When autonomous technologies control Gregg Freeby, American Segmental Bridge Institute bridges and highways. vehicles, exceeding the speed limit will not be an option. Pete Fosnough, Epoxy Interest Group of the One crucial variable in bridge design is the Researchers are currently engaged in studies to Concrete Reinforcing Steel Institute fleet of vehicles that will be on the roads in future model how emerging vehicular technologies will affect Alpa Swinger, Portland Cement Association decades. Trend watchers predict that electric vehicles the functioning of households, and they have already Miroslav Vejvoda, Post-Tensioning Institute will be one-third of the inventory by 2040 and one- noted differences between urban and rural areas of Cover half of the inventory by 2050. They also anticipate the United States. In some cases, autonomous vehicles DYWIDAG-Systems International provided the that autonomous vehicles will be on the roads soon, and phone-based applications will likely select routes post-tensioning for the Gerald Desmond Bridge although the widespread impact of these vehicles on the that are not on the current mainline arterials, perhaps in Long Beach, Calif. Photo: DYWIDAG-Systems transportation network is harder to predict.1 to avoid tolls or heavy traffic. At the same time, our International. vehicles and phones will collect data on our driving Ad Sales routines and preferences and use that information to Jim Oestmann make subsequent decisions about what routes to take Phone: (847) 924-5497 and what tolls will be incurred. Fax: (847) 389-6781 • [email protected] Pilot projects in Colorado and Ohio will answer some Reprints questions about vehicle-to-vehicle and vehicle-to-road Lisa Scacco • [email protected] communications. As we gather insights, we’ll need to Emerging vehicular technology promises to decide what capital programs will be needed to make Publisher change human habits in ways that will directly affect the transportation system of the future work. Now is a Precast/Prestressed Concrete Institute transportation solutions, including fundamental aspects great time for bridge engineers to get engaged so we Bob Risser, President of bridge design such as lane geometry and access can understand how new technologies will influence Postmaster: Send address changes to ASPIRE, 200 W. Adams St., Suite 2100, Chicago, IL 60606. Standard postage paid at Chicago, IL, points. For example, commuters may not care so much our roadways, bridges, and interchanges. This is also and additional mailing offices. ASPIRE (Vol. 13, No. 2), ISSN 1935-2093 is published quarterly by the about personal time spent in traffic if they can relax the time to start reviewing the design assumptions Precast/Prestressed Concrete Institute. while their autonomous cars drive them home. Their underlying our bridge codes. Will our investment in Copyright 2019, Precast/Prestressed Concrete Institute. incentive to pay tolls for express lanes or to use managed variable toll rate commuter lanes with bridge assets If you have a suggestion for a project or topic to be considered for ASPIRE, please send an email to [email protected] lanes restricted to passenger vehicles may therefore become a feature whose use will need to be redefined decline. But parcel delivery businesses might be willing to carry heavier trucks or platoons of trucks? With to pay a premium to access faster lanes and bridges and connected vehicles, like a platoon of trucks, what bridge Reference shorten the time that their vehicles spend in traffic. code design assumptions will need to be revisited and I also wonder whether we will soon be designing how will these new load effects be reconciled with the 1. SP Global. 2018. The Road Ahead for Autonomous bridges for mass-transit, fixed-guide systems with ride- inherent capacity of our existing inventory? I certainly Vehicles. International Bridge, Tunnel and share and autonomous-vehicle technologies. If so, we hope our bridge colleagues in leadership roles are Turnpike Association. https://www.ibtta.org/studies- may need to revisit older transportation solutions. For helping to identify consistent and prudent strategies. and-reports.

American Segmental Bridge Institute Epoxy Interest Group Expanded Shale Clay and Slate Institute

Portland Cement Association Precast/Prestressed Concrete Institute Post-Tensioning Institute Wire Reinforcement Institute 2 | ASPIRE Spring 2019 Accelerating Accelerating With collaborative planning and delivery, Success quality, reduced construction time elements paveelements the way for improved designsour smart using precast and alonger service life. the Governor Mario M. Cuomo Bridge in NY NY in Bridge Cuomo M. Mario Governor the and the Bonner Bridge Replacement in NC. in Replacement Bridge Bonner the and Precast concrete drove the success of of success the drove concrete Precast hdrinc.com hdrinc.com

Photo Credit: New York State Thruway Authority EDITORIAL CONCRETE CALENDAR 2019–2020 CONTRIBUTING AUTHORS For links to websites, email addresses, or telephone numbers for these events, go to www.aspirebridge.org and select the Events tab.

Dr. Oguzhan Bayrak is a professor at the April 8, 2019 July 22–25, 2019 University of at ASBI Grouting Certification BEI–2019 (Bridge Engineering Austin. Bayrak was inducted Training Course Institute Conference) into the university’s J.J Pickle Research Campus Hyatt Regency Waikiki Academy of Distinguished Austin, Tex. Honolulu, Teachers in 2014. April 8–10, 2019 August 4–7, 2019 DBIA Design-Build for AASHTO Committee on Materials Dr. Benjamin A. Transportation Conference and Pavements Annual Meeting Graybeal is the team Duke Energy Convention Center Four Seasons Hotel Baltimore leader for bridge Cincinnati, Ohio Baltimore, Md. engineering research within the U.S. Federal April 24–26, 2019 September 4–6, 2019 Highway Administration’s PTI Level 1 & 2 Multistrand and Western Bridge Engineers’ Seminar (FHWA’s) Office of Grouted PT Specialist Workshop Boise Centre Infrastructure Research in Baltimore, Md. Boise, Idaho Washington, D.C. He also leads the structural concrete research program for FHWA. April 27, 2019 September 22–25, 2019 PTI Level 1 & 2 Multistrand and AREMA Annual Conference Dr. Jeremy Gregory is a Grouted PT Inspector Workshop Convention Center research scientist at MIT Baltimore, Md. Minneapolis, Minn. and the Executive Director of the MIT Concrete May 5–8, 2019 September 25–28, 2019 Sustainability Hub. Dr. PTI 2019 Convention & Expo PCI Committee Days and Technical Gregory studies the Hyatt Regency Seattle Conference featuring the National economic and environmen- Seattle, Wash. Bridge Conference tal implications of Loews Chicago O’Hare Hotel engineering and system design decisions, May 27–29, 2019 Rosemont, Ill. particularly in the area of materials production fib Symposium 2019 and recovery systems. Krakow, Poland October 1–4, 2019 Frederick Gottemoeller PTI Committee Days is an engineer and architect June 2–5, 2019 Hilton Santa Fe Historic Plaza who specializes in the Second International Interactive Santa Fe, N.Mex. aesthetic aspects of bridges Symposium on Ultra-High- and highways. He is the Performance Concrete October 20–24, 2019 author of Bridgescape and Hilton Albany ACI Fall 2019 Conference was deputy administrator of Albany, N.Y. Duke Energy Convention Center & the Maryland State Hyatt Regency Cincinnati Highway Administration. June 10–13, 2019 Cincinnati, Ohio Dr. Zachary Haber International Bridge Conference is a research structural Gaylord National Resort and November 4–6, 2019 engineer with the bridge Convention Center ASBI 31st Annual Convention and engineering research within National Harbor, Md. Committee Meetings the U.S. Federal Highway Disney’s Contemporary Resort and Administration’s Office of June 24–27, 2019 Grand Floridian Resort Infrastructure in AASHTO Committee on Bridges Lake Buena Vista, Fla. Washington, D.C and Structures Annual Meeting Renaissance Montgomery Hotel at the December 11–13, 2019 Dr. Bruce W. Russell Convention Center International Accelerated Bridge is director of the Bert Montgomery, Ala. Construction Conference Cooper Engineering Hyatt Regency Miami Laboratory and an associate June 28–29, 2019 Miami, Fla. professor of civil and PTI Level 3 Unbonded PT Repair, environmental engineering Rehabilitation, and Strengthening January 12–16, 2020 at Oklahoma State Workshop Transportation Research Board University. He has been a Chicago, Ill. Annual Meeting PCI member since 1990, and currently serves on the Walter E. Washington Convention PCI Technical Activities Council and the PCI Center Bridges, Concrete Materials, and Fire Committees. Washington, D.C.

4 |4 ASPIRE | ASPIRE Spring Spring 2019 2019 www.dsiamerica.com

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ASPIRE Spring 2019 | 5 FFOCUSO C U S Changing Perceptions

DYWIDAG-Systems International’s new high-tech inspection and monitoring tools add to its selection of post-tensioning products and services, enhancing its role as a specialty contractor.

by Craig A. Shutt

While DYWIDAG-Systems International “Clients don’t see a difference in the (DSI) is best known for its array of post- ‘We’re no longer way they interact with us,” Caravello tensioning and geotechnical products, just the post-tensioning notes of the reorganization. “But it its role as a specialty contractor has gives us new efficiencies and initiatives been growing. Now, with the addition product supplier that for expansion.” Those efforts are of several high-tech companies, DSI people knew in the being aided by recent domestic and intends to expand its prominence and international acquisitions: market penetration as a service provider. past.’ • In October 2017, DSI Construction announced a strategic partnership New Scope of Services Many recent changes at DSI began after in the United States with “We’re no longer just the post- Matti Kuivalainen was appointed chief Infrastructure Preservation Corp., tensioning product supplier that executive officer of DSI Construction in a robotic engineering firm, to people knew in the past,” says the United States in September 2017. develop technology to aid in the Jason Caravello, director of business DSI Construction was split from DSI nondestructive inspection of bridges. operations for DSI’s Global Services Underground the previous year by the • In March 2018, the parent company business unit in North America. Germany-based parent company DSI. acquired Alpin Technik und “For example, we are active in In January 2018, the North American Ingenieurservice, which provides the inspection, restoration, and divisions were organized into the Global robotic inspection and maintenance maintenance of parking structures, Services (contracting), Geotechnical, of infrastructure. Services include stadiums, high-rise buildings, tanks, Post-Tensioning, and Concrete corrosion protection, special and bridges. We are experts at Accessories business units. Global assemblies, and repairs. design-build structural-strengthening Services focuses on three key service • In October 2018, the parent solutions, often utilizing a variety of offerings: repair and strengthening company acquired Datum Group, systems, including post-tensioning or for structures, robotic inspections, and a global monitoring company CFRP [carbon-fiber-reinforced polymer], infrastructure health monitoring, which that performs structural health– and even coatings. We obviously use includes cloud-based data acquisition monitoring services to enhance our products where they apply, but we for structural predictive analysis, among safety, sustainability, and cost do much more than that.” other services. savings.

DYWIDAG-Systems International (DSI) was hired to inspect, upgrade, and repair the external post-tensioning systems for the 14.3-mile-long Y Interchange in San Antonio, Tex. DSI developed repair protocols using borescopes and specialized vacuum-grouting techniques. All Photos: DSI. “We hope to see significant growth in our capabilities for doing robotic inspections and repairs for tendons and cable stays,” Caravello says. The robots can move along cables to make polyethylene repairs, perform water-jet cleaning, inspect via camera links, and document conditions in high resolution. “It’s cutting-edge technology.” Installation of a split-duct system for permanent repair of external tendons for the Y Interchange project in San Antonio, Tex. According to Caravello, the international companies will provide expertise to the toolbox and allow us to bring more work. DSI logged more than 75,000 U.S. division, and DSI plans to ramp up services to the table.” work hours to complete the project. development throughout 2019. DSI has already used the robotic systems on the Growth in the Repair Market Post-Tensioning Expertise cable-stayed Fred Hartman Bridge in The repair market is growing DSI’s new offerings will enhance the Houston, Tex., with excellent results, he substantially as states look to maximize company’s existing expertise in post- notes. the service life of bridges in an era of tensioning services and products. “Post- limited federal funding. “It’s a critical tensioning is becoming more popular Caravello acknowledges that robotic market that’s really growing substantially and mainstream across the country,” inspection technology is still developing. and yields good opportunities even in says Joseph Salvadori, former Eastern “But we’re very excited about the tough economic times.” U.S. regional manager for the Post- potential,” he says. “It offers ways to Tensioning & Reinforcing business unit. do inspections and repairs that are more An example of DSI’s repair work can be “We are seeing more segmental designs efficient and safer.” Drones can do seen in its services for the Y Interchange that need our products.” some of that inspection work, he notes, in San Antonio, Tex. The 14.3-mile-long but their use raises liability issues related elevated , built in the 1980s to ‘Post-tensioning is to their potential to distract traffic and merge Interstates 35 and 10, used 755 the challenges of controlling them in precast concrete segmental box-girder becoming more popular wind currents. “We think robotic spans post-tensioned with longitudinal and mainstream across options offer much more potential.” and transverse tendons. In 2014, DSI was hired to inspect, upgrade, and repair the the country.’ The Datum Group acquisition offers external post-tensioning systems. The trend offers great potential on DSI the opportunity to expand health- the West Coast, where the company monitoring services, especially for railroad The project involved distinctive primarily works as a post-tensioning structures, an area of specialization challenges. “When the bridge was built, subcontractor. “California and the West for the U.K.-based company. “Using project specifications did not reflect are largely supply-and-install markets,” inclinometers, accelerometers, and the importance of properly grouted says Bryan Lampe, U.S. Western regional specialized sensors to gain real-time data tendons,” says Caravello. Also, bridge manager for the Post-Tensioning on performance provides a clearer picture construction was completed in three & Reinforcing unit. “Many DOTs of a bridge’s status,” says Caravello. phases using three design/construction [departments of transportation] and the The firm monitors assets on highways teams and post-tensioning suppliers. DSI FHWA [Federal Highway Administration] and railroads internationally to assess inspected the anchors and tendons of are focusing attention on quality control performance of aging infrastructure, each of the three phases and developed of post-tensioning and the certification according to former Datum Group owner repair protocols using borescopes and of field personnel, and most general Rory O’Rourke. Its cloud-based database, specialized vacuum-grouting techniques contractors are not equipped to perform Platform Interactive, harvests, validates, that measured void volumes and then this work. As a result, we see an interprets, and presents data from any filled the voids with grout. expansion of our installation work here source. The firm’s latest addition is an and in states like Texas and Florida.” automated pile static-load testing system For external ducts that had incurred that can remotely apply a load up to 30 major damage over the years through For example, DSI is providing MN (6750 kip) to a pile. Used in Europe splitting or cracking, DSI designed and longitudinal and transverse post- for some time, the system was recently installed a special split-duct system for tensioning for the cast-in-place shipped to its first U.S. customer. permanent repair. Gaining access inside segmental box-girder approach spans the precast concrete segments was a for the 5134-ft-long Gerald Desmond These new technologies and expertise major challenge, Caravello notes. It Bridge in Long Beach, Calif. This bridge will be developed and marketed in the was done from beneath the segments is currently under construction and coming months, Caravello says. “There through integrated hatches, which were will be, when completed, the second- will be a period of development, but often located directly above heavy traffic highest cable-stayed bridge in the they add some high-tech tools to our areas, requiring traffic control and night United States. The spans are being

ASPIRE Spring 2019 | 7 The cantilever and continuity post- tensioning consisted of eight tendons with twelve 0.6-in.-diameter strands, 57 tendons with nineteen 0.6-in.-diameter strands, and 90 tendons with twenty- seven 0.6-in.-diameter strands, all of which used corrugated polypropylene ducts. The design also utilized permanent 36-mm-diameter (1.4-in.-diameter) Grade 150 threaded-bar tendons for longitudinal post-tensioning in the superstructure and in the tops of piers.

“There are always challenges with major projects, but Brattleboro was successful for both DSI and the contractor, with no major hiccups,” Salvadori says. DSI is currently undertaking a growth initiative to expand the scope of its programs to furnish and install products in the DYWIDAG-Systems International is providing longitudinal and transverse post- Eastern region, he notes. tensioning for the cast-in-place segmental box girder approach spans for the 5134-ft-long Gerald Desmond Bridge in Long Beach, Calif. The spans are being Upholding Grouting constructed using a movable scaffolding system, its first use in the state. Standards constructed using a movable scaffolding strand post-tensioning products for To ensure its expertise can extend a system, its first use in the United States. the Interstate 91 Brattleboro Bridge bridge’s service life, DSI prefers to do its in Brattleboro, Vt. This design-build own grouting installations. Nationally, The typical span uses four or five project in an environmentally sensitive requirements have definitely become tendons with twenty-seven 0.6-in.- area featured cast-in-place segmental more stringent since bridges like the diameter strands running full length in construction using the balanced- San Antonio Y Interchange were built. each girder web. Partial-length strand cantilever method with a form traveler “Today, grouting specifications are a key tendons, typically twenty-seven or (see the Project article in the Spring focus for designers and contractors,” thirty-seven 0.6-in.-diameter strands, 2018 issue of ASPIRE®). The three-span, says Caravello. “They understand the pass longitudinally through the top 1036-ft-long structure employed a value it [grouting] provides.” decks, which are also transversely post- straightforward post-tensioning design tensioned using tendons with four with only minor variations, Salvadori Lampe agrees. “Owners and designers 0.6-in.-diameter strands in flat ducts says. The 814 transverse tendons in understand today that grouting is a with flat anchorages. Several units the top slab used four 0.6-in.-diameter critical component to the durability of feature partial-length tendons that strand flat-anchor bodies with stainless a structure. It’s become an area of focus required tensioning from within the box steel local-zone anchor reinforcement. in the past 15 years, with significant girder’s interior, which was achieved Electrically isolated tendons (EITs) were included in the top tendon (of four) in each through close collaboration with the of the five girder lines making up the main channel unit of the Coplay-Northampton contractor. Bridge between the Pennsylvania boroughs of Coplay and Northampton. Their use in this bridge marks the first application of EITs in the United States. On the Desmond project, DSI has already installed more than 3300 tons of bonded tendons ranging in size from four to thirty-seven 0.6-in.-diameter strands with anchorages. In all, nearly 10 million ft or about 7.3 million lb of tendons will be installed. DSI has also performed tensioning and grouting operations, including transverse deck post-tensioning. DSI’s work on this project will be completed in mid-2019.

On the East Coast, where general contractors typically undertake post- tensioning duties, DSI’s most frequent role remains that of product supplier. For example, DSI supplied its multi-

8 | ASPIRE Spring 2019 upgrades to standards along with awareness and training on techniques and inspections. Grouting used to be an afterthought, and that’s changed. Now it’s recognized as arguably the most important element.”

Execution is at least as important as specifications, he notes. “In the Western United States, post-tensioning is performed almost exclusively by specialty subcontractors, and their field Post-tensioning strands have been installed and tensioning operations are underway personnel have extensive expertise. for the main spliced-girder unit on the Coplay-Northampton Bridge between the Workmanship is often the weak link, Pennsylvania boroughs of Coplay and Northampton. and it’s critical. We’re also seeing a major push to revise grout materials Approval Guideline1)-approved anchors. goal. “We see these new technologies and methods and focus more attention An EIT was installed as the top tendon as a way to pull us into the market with on new technologies, which will help (of four) in each of the five girders. expanded services,” says Caravello. extend the structure’s life.” “The EITs provide the highest level of “We want the industry to see DSI as a corrosion protection possible, as they bridge-repair contractor as well as a post- ‘Owners and isolate the strands completely so no tensioning product supplier. It’s hard to electrical path exists from the strand to change perceptions, but we expect that designers understand the structural concrete for corrosion to to change as our offerings grow.” today that grouting is a develop,” Salvadori explains. Reference critical component to the Engineers at Lehigh University deployed 1. European Organisation for Technical durability of a structure.’ a monitoring system for impedance Approvals (EOTA). 1997. Metal and capacitance, which is intended to Anchors for Use in Concrete. Innovation provide an indication of performance of European Technical Approval New technology was a key element of the corrosion protection system. Initial Guideline (ETAG) 001. Brussels, the design for the Coplay-Northampton results at 28 days met expectations, and Belgium: EOTA. Bridge in Coplay, Pa. The eight-span, designers expect electrical resistance 1118-ft-long precast concrete girder readings will rise as the grout ages. A bridge features a three-span (181-181- significant drop in resistance would DSI’s 150-Plus Years of 186 ft), continuous post-tensioned, be indicative of leakage or ingress of Service spliced prestressed concrete bulb-tee moisture. girder river crossing, the first of its type Dyckerhoff & Widmann AG, later in the state. Five girder lines make up DSI participated in an FHWA-sponsored shortened to DYWIDAG International and the main channel unit cross section, workshop on the EIT technology hosted then to DYWIDAG Systems-International with girders in the pier segments varying by Lehigh University in October 2018, (DSI), was founded in 1865 as Lang & in depth from 6 ft 7 in., the depth of shortly after the last tendon was grouted. Cie by German concrete manufacturer the constant depth drop-in and end DSI is also looking to help update Wilhelm Gustav Dyckerhoff. The segments, to 9 ft 7 in. at the piers. All specifications related to EIT anchoring company’s name and business strategy girders are made continuous by four and duct ventilation. (For more changed in 1866 when Dyckerhoff’s son, longitudinal post-tensioning tendons information on EITs, see the Concrete Eugen, joined forces with his father-in- with fifteen 0.6-in.-diameter strands. Bridge Technology article in this issue of law, Gottlieb Widmann, to refocus on ASPIRE on page 36.) construction engineering. DSI supplied engineering services, materials, and field-installation DSI is also focusing on ways to strengthen The firm worked on some of Europe’s contracting for this project. It also members with carbon fibers and meet earliest rammed-concrete bridges and installed electrically isolated tendons seismic requirements with AASHTO-type developed an array of products and (EITs). This installation, which was girders. The need to control long-term technical innovations for post-tensioning requested by FHWA as a demonstration strand costs to reduce market volatility concrete. By the 1950s, it was offering project, was the first use of EIT and allow for more precise cost estimates licenses and consulting contracts for technology in the United States and its also remains a key need, Salvadori its products and construction methods first use ever in a bridge with spliced notes. “Challenges will always arise, around the world. precast, pretensioned concrete girders. and we intend to continue to work on improvements and advances.” The firm employs about 2300 people Because domestic electrically isolated worldwide. For more on its history, see anchor bodies are not available, DSI Innovative approaches provided by its the Partner Spotlight in the Summer 2016 used its own ETAG (European Technical new partnerships will help DSI reach that issue of ASPIRE.

ASPIRE Spring 2019 | 9 PERSPECTIVE Quantitative Assessment of Resilience and Sustainability

by Dr. Jeremy Gregory, Massachusetts Institute of Technology

Sustainability is a word that is conditions is a measure of resilience that quake shattered roads and bridges, ubiquitous, yet often vague. At the is vital to understanding sustainability, destroyed neighborhoods, disrupted Massachusetts Institute of Technology particularly in regions where climate- livelihoods, and killed an estimated 139 Concrete Sustainability Hub (CSHub), related events are becoming increasingly people.3 In response to the earthquake, we have a concise mantra: “We want frequent and destructive. authorities established more rigorous our world to last.” This saying helps us building codes intended to protect clarify what we mean by sustainability Resilience, an important element of buildings from future seismic activity. with regard to the structures we build, sustainability, can be quantifiably Alaska’s successful response to the 2018 including bridges. Such structures measured in two stages, response earthquake is due, in large part, to the will remain sustainable only if civil and recovery (Fig. 1). First, we assess changes implemented in building and engineers are farsighted. Many aspects the system’s immediate response to bridge design codes.1 of a structure, including its future an event. For example, let’s imagine economic impact and the environmental that a city experiences a hurricane. Alaska’s rapid recovery demonstrates conequences of construction, repairs, Before the storm arrives, the city how efforts to improve resilience can or replacement, affect its sustainability. operates at peak performance, as deliver a return on investment (ROI). Our research finds that quantitative indicated by parameters like economic If stakeholders remain unaware of assessment of these factors can lead to productivity, transportation efficiency, the ROI of resilience, success stories alternatives that improve a structure’s and so on. As the storm ensues, the like that of Alaska in 2018 will occur sustainability (see http://cshub.mit.edu/ city’s performance will drop because less frequently. Calculating this ROI news/lca-research-brief-quantifying- of economic inactivity, disabled is therefore a key aspect of CSHub’s hazard-life-cycle-cost for more infrastructure, and other damages. work, and, to do it, a probabilistic information). The extent of the drop in performance hazard repair estimation model has is the first measure of resilience—a been developed. Sustainability analyses are usually smaller reduction in performance conducted by considering a structure’s indicates greater resilience. The second The crux of this model is the probability typical loading conditions throughout measure of resilience is the time to curve, which allows us to analyze the its life. An additional important recovery to a performance level that uncertainties of disaster and predict consideration is the structure’s response may be lower than, the same as, or outcomes. Using government and to atypical loading conditions, such as higher than the performance level other scientific data, we can generate those caused by natural or human-made before the disaster. A rapid and strong a probability curve that estimates disasters. A structure’s response to such recovery signifies effective resilience. the likelihood of a hazard in a given location. We refer to this as a hazard A recent example of resilience can curve (Fig. 2). be seen in the aftermath of Alaska’s November 2018 7.0-magnitude The hazard curve’s counterpart in earthquake. While the photos of resilience analyses is the fragility curve crumbled highways were dramatic, the (Fig. 3), which estimates the damage actual devastation was not extensive. a hazard will inflict on a structure. To Authorities reported no fatalities and generate fragility curves, we employ no collapsed buildings, and seriously a technique inspired by molecular damaged roadways were repaired dynamics. We model the integrity of a within days.1,2 Pundits therefore structure’s components like we would declared the state’s response to the the bonds of atoms. This methodology disaster a success. allows us to efficiently estimate the effects of hazard-induced loads on Figure 1. Resilience has two parts—initial Alaska has not always enjoyed these components. What makes this response to a damaging event (the drop such resilience. In 1964, the state technique unique is its versatility in performance) and recovery time. All experienced the largest earthquake and precision. Whereas conventional Figures: Dr. Jeremy Gregory. in U.S. history. This 9.2-magnitude models of building fragility approximate

10 | ASPIRE Spring 2019 damage for a broad class of buildings, we can efficiently generate fragility curves of the damage to different elements of specific building designs. Fragility curves for specific building designs give stakeholders a more detailed and quantitative understanding of building damage for proposed mitigation solutions.

By integrating hazard and fragility curves, we can create a comprehensive damage model that assesses potential damage from hazards of different intensities. When we assign costs to these damages and add them to the normal lifetime maintenance and construction costs of a structure as part of a life-cycle cost analysis, we can determine whether investments in resilience will prove cost effective over a structure’s life when compared to conventional designs.

Our research has shown that the value of hazard resistance can be quantified and that investments in hazard mitigation can pay off, particularly in locations where hazard repair fixed its earthquake-shattered roads costs approach the value of initial References in just days.” The Verge website. construction costs. Within expectation 1. Bressan, D. 2018. “How the 1964 December 8, 2018. https://www. of sustainable infrastructure, such Good Friday earthquake helped theverge.com/2018/12/8/18128983/ resilience analyses for structures, Anchorage withstand last Friday’s alaska-earthquake-roads-fixed- including bridges, are critical. It is quake.” Forbes. December 4, 2018. anchorage-damage. essential that we create a culture of https://www.forbes.com/sites/ 3. Taylor, A. 2014. “1964: Alaska’s resilience by educating stakeholders davidbressan/2018/12/04/how- Good Friday earthquake” that quantitative resilience assessments the-1964-good-friday-earthquake- The Atlantic. May 30, 2014. are possible and necessary for helped-anchorage-withstand-last- https://www.theatlantic.com/ infrastructure. Bridge engineers are well fridays-quake/#5dfd42503a98. photo/2014/05/1964-alaskas-good- positioned to carry this mantle. 2. Griggs, M.B. 2018. “How Alaska friday-earthquake/100746.

Figure 2. A generic hazard curve. Figure 3. A generic fragility curve.

ASPIRE Spring 2019 | 11 PROJECT REHABILITATING MARYLAND ROUTE 195 (CARROLL AVENUE) BRIDGE OVER SLIGO CREEK

by Fred Braerman, Johnson, Mirmiran & Thompson, and Maurice Agostino, Maryland Department of Transportation, State Highway Administration

The Maryland Route 195 (Carroll Avenue) Sligo Creek, and a county-owned trail access to all four approaches to the Bridge over Sligo Creek, located in the for hiking and biking. In 2011, the bridge. Washington, D.C., suburb of Takoma MDOT State Highway Administration Park, Md., is a nonredundant, open- (SHA) Office of Structures contracted During the planning stage, several spandrel, reinforced concrete the bridge design engineer to project-specific challenges were noted. that carries one lane of traffic in each perform an in-depth field inspection, The bridge’s location, 50 ft over a ravine direction, with sidewalks on both sides. structural analysis, and assessment of within the floodplain of Sligo Creek, Nearly 80 years after being constructed the bridge. Because the bridge was constrained the project site. Existing in 1932, the bridge became rated eligible for inclusion on the Historic utilities on the bridge and adjacent structurally deficient in 2011, when Register and on MDOT SHA’s Priority 1 overhead utilities on the west side of routine inspections found extensive and list for preservation, the bridge design bridge would have to be temporarily worsening deterioration of the bridge engineer focused on rehabilitation relocated to allow for construction. deck. While evaluating options for this strategies. Sligo Creek Parkway, located beneath aging structure, Maryland Department of the southernmost span, was a major Transportation (MDOT) officials recognized The bridge design engineer’s findings commuter route within this congested the functional and historic significance of indicated that replacement of all suburb, and a heavily used hiker-biker the bridge and concluded that replacing it portions of the bridge above the arch trail located beneath the northernmost with a girder-type structure would not be ribs would be required to address the span would need to remain open the right solution. Instead, MDOT decided extensive deterioration of the deck, floor during rehabilitation. that rehabilitation was the appropriate beams, columns, and spandrel arches. strategy, a decision that was well received The plan was to repair and preserve the Project leaders conducted extensive by the community. A construction existing substructure units and arches public outreach to gain input and contract was awarded to the prime while reconstructing the remainder of support from the community. For contractor for $9.3 million in October the bridge from the arch ribs up. The example, they held multiple public 2015, and the project was completed less complete reconstruction of the bridge meetings and coordinated plans with than one year after the bridge was closed above the arch ribs would allow for the Washington Adventist Hospital on the to traffic. The bridge was reopened ahead structure to be widened curb-to-curb by north side of the bridge, the Takoma of schedule in June 2017. 2 ft, creating 11-ft-wide travel lanes. The Park City Council, the Montgomery community wanted wide shoulders to County Transit bus system, Montgomery Planning and the make biking safer in this residential area. County Parks, and local emergency Decision Process responders. Originally built with non-air-entrained Additionally, the rehabilitation would concrete and black reinforcing steel, include new sidewalks on both sides Design Challenges the 220-ft-long Carroll Avenue Bridge of the bridge, with new sections of When a bridge is rehabilitated, its has span lengths of 65, 90, and 65 sidewalk extending past the ends of the geometry must be maintained. The ft and traverses Sligo Creek Parkway, bridge to provide improved pedestrian existing Carroll Avenue Bridge was

MARYLAND ROUTE 195 (CARROLL AVENUE) BRIDGE OVER SLIGO CREEK / profile TAKOMA PARK, MARYLAND BRIDGE DESIGN ENGINEER FOR REHABILITATION: Johnson, Mirmiran & Thompson, Hunt Valley, Md. PRIME CONTRACTOR: Kiewit Infrastructure South, Omaha, Neb. REINFORCING STEEL SUPPLIER: Gerdau, York, Pa. OTHER CONSULTANTS (ROADWAY AND TRAFFIC DESIGN): Mercado Consultants Inc., Ashton, Md.; Sabra and Associates Inc., Columbia, Md.

12 | ASPIRE Spring 2019 Debris accumulation on the demolition SHA required the contractor to provide identically. However, details could not shield /work platform. Polystyrene a 295-ft-long temporary pedestrian be exactly matched for the existing protects the arches from debris. All bridge along the east side of Carroll open-balustrade railings, which were Photos: Johnson, Mirmiran & Thompson. Avenue. significant to the Maryland Historical Trust. Fortunately, the Texas Department A major structural concern involved of Transportation Traffic Railing Type maintaining a balanced-loading C411, which was crash tested and met condition during the sequence of the test requirements for the design demolition and build back to avoid speed and classification of Carroll overstressing the existing arches that Avenue, closely resembled the existing were to remain. The project leaders railings. This barrier received approval were especially mindful of this issue without comment. because three workers had died on this site in 1932, when a previous Construction reinforced concrete bridge built in The primary construction challenge for 1904 collapsed during demolition prior the project was access. Steep side slopes to construction of the arch bridge.1,2 at each end of the bridge precluded In the rehabilitation project, every the provision of construction entrances on the crest of a vertical curve, which precaution was taken to ensure safe from Carroll Avenue. The solution resulted in a sump at each abutment conditions. The contract plans included was to provide an entrance off Sligo just past the end of the bridge. The City requirements for a 22-stage systematic Creek Parkway; however, this location of Takoma Park requested that drainage construction sequence working from complicated matters because the improvements be made to alleviate the center of each arch outward in a parkway also served as the temporary flooding from these sumps. During concentric fashion about the crown detour route. Flaggers were employed design, the bridge design engineer of the arch. A structural analysis was daily to facilitate traffic flow while found that the existing sump inlets performed using software under each construction vehicles entered and exited were severely undersized as the result of condition of demolition and build the site. increased development over the years. back to verify that the arches were not The inlets were therefore replaced with overstressed during any of the stages. One of the construction innovations larger, more efficient curb-opening-at- that made the project such a success grade inlets to minimize the potential The reconstruction plans were was the prime contractor’s use of a for flooding in the future. painstaking in recreating and replicating work platform at the elevation of the the details of the existing bridge, arch supports. This work/demolition Maintenance of traffic during which included extensive architectural platform consisted of steel beams and reconstruction of the cast-in-place features for the spandrel arches, floor timber flooring supported by shoring reinforced concrete bridge was a beam overhangs, and columns. These towers 15 to 20 ft above the floodplain significant challenge. Unlike a typical architectural details were matched of Sligo Creek. This platform solved redundant, multi-girder bridge arrangement, removing one of the two Concrete being placed for new floor beams at the top of one of the arches. arches during a staged construction scheme would render the bridge unstable. After this inherent problem with the structure configuration was explained to the stakeholders, all parties agreed that closing the bridge during construction and detouring traffic was the only feasible construction solution. However, this decision presented a problem for pedestrians because there was no alternative way to safely cross the ravine on foot. Therefore, MDOT

MARYLAND DEPARTMENT OF TRANSPORTATION STATE HIGHWAY ADMINISTRATION, OWNER BRIDGE DESCRIPTION: Three-span, 220-ft-long, open-spandrel concrete arch STRUCTURAL COMPONENTS: Repair of substructure units and arch ribs and replacement of columns, floor beams, and deck using 712 yd3 of concrete MDOT SHA Mix No. 6 (28-day compressive strength of 4500 psi); 64 yd3 of concrete MDOT SHA Mix No. 3 (28-day compressive strength of 3500 psi); 172,000 lb of epoxy-coated reinforcing steel; and 15,000 lb of black reinforcing steel BRIDGE CONSTRUCTION COST: $9.3 million AWARDS: American Council of Engineering Companies Maryland 2018 Outstanding Project Award; Portland Cement Association 16th Concrete Bridge Awards (2018) Award of Excellence

ASPIRE Spring 2019 | 13 All superstructure concrete consisted of MDOT SHA Mix No. 6 (which has a 28-day concrete compressive strength of 4500 psi). All reinforcing steel in the deck slab, floor beams, bridge barrier, and sidewalks on the bridge was epoxy coated. To extend the life of the new bridge deck slab, an epoxy-polymer concrete overlay was applied after the bridge deck slab was fully cured.

Pervious concrete was used on the sidewalk approaches to the bridge. This porous concrete feature allowed for stormwater infiltration and minimized Rendering of proposed bridge section shows roadway with space for bicycles and runoff, providing additional stormwater sidewalks for pedestrians. Figure: Maryland Department of Transportation, State management, which was considered a Highway Administration. value-added improvement for the project because the project was exempt from the problem of trying to work on the the abutments of the bridge. However, stormwater management improvements uneven terrain beneath the bridge bringing in a concrete pump truck was per state requirements. and greatly facilitated construction not economical for placing the small demolition and build back. It also volume of concrete needed for the References minimized the project’s environmental short columns. Instead, the concrete 1. “Three Men Killed As Bridge impact. As concrete was demolished placements were made in a fashion Crashes at Takoma Park.” and dropped to the platform, small similar to the original construction in Montgomery News-Advocate, excavators transferred the material to 1932, with workers lifting buckets and January 13, 1932. the staging area, where the reinforcing placing concrete by hand. 2. Hendrix, Steve. 2016. “Three steel was separated and loaded onto Workers Once Died Rebuilding trucks for hauling. Design Criteria and This Historic Md. Bridge. Now Materials a New Makeover Is Under Way.” The contractor made extensive use of All new elements of the bridge were Washington Post, May 13, 2016. polystyrene during demolition of the designed in accordance with American existing superstructure to protect the Association of State Highway and ______existing arches during construction Transportation Officials’ AASHTO LRFD Fred Braerman is vice president, and provide fillers in the formwork for Bridge Design Specifications, sixth edition. structures transportation, for Johnson, creating the architectural details on the The existing arches and substructure Mirmiran & Thompson in Hunt Valley, floor-beam overhangs, spandrel arches, units were analyzed and load-rated Md., and Maurice Agostino is deputy and openings in the bridge railing. Most in accordance with allowable stress director, Maryland Department of the new concrete for the floor beams design methods, which more accurately of Transportation, State Highway and deck slab was pumped from behind correlated to the original design. Administration, in Baltimore, Md.

View of completed Carroll Avenue Bridge from Sligo Creek trail. PCI Offers FREE Bridge Geometry Manual and Training A Bridge Geometry Manual has been developed as a FREE resource that presents the basics of roadway geometry and many of the calculations required to define the geometry and associated dimensions of bridges. Four FREE instructor-led training (ILT) courses have been developed to facilitate the use of the Bridge Geometry Manual. The target audience for the Bridge Geometry Manual and instructor-led training courses is bridge engineers with two or less years of experience and CAD tech- nicians who have not had previous training in roadway and bridge geometry. Again, there is no cost to enroll in and complete any of these courses being taught by the contracted primary author Corven Engineering Inc. or to download the new manual. Register for these ILT Courses Go to pci.org/PCI/Education/Webinars

Fundamentals of Roadway Geometry (T505) on April 16, 2019 at 2:00 PM Eastern time Fundamental to establishing bridge geometry and the resulting geometry and dimensions of bridges is the ability to work with roadway geometry provided by highway designers. Terminology used in roadway geometry is discussed. The three primary aspects of roadway geometry (horizontal alignment, vertical profile, and cross-section super elevations) are presented in this course. Stationing along horizontal alignments is also defined. Mathematical formulae and graphical representations are presented to define these three primary aspects, along with worked example problems.

Working with Horizontal Alignments (T510) on April 30, 2019 at 2:00 PM Eastern time Locating points along or offset from a horizontal alignment is necessary to defining bridge geometry. This course presents a vector-based approach to locating the North and East coordinates of point defined by a horizontal alignment. The vec- tor-based approach was taken as it closely follows the way CAD software is used. Vector solutions are presented for 1) Locating points on tangent runs and circular curves, 2) Locating points offset from tangent runs and circular curves, and 3) Project points onto a tangent run or circular curve.

Geometry of Straight Bridges (T515) on May 14, 2019 at 2:00 PM Eastern time The third course begins by introducing terminology common to bridges elements. The material presented in the first two courses is then used to define the geometry of straight bridges. Concepts of skew crossings and the impact on bridge ge- ometry are presented. Haunches that are cast over girders along with the bridge deck are defined. Factors effecting haunch thickness are defined using mathematical equations, which are demonstrated through examples. Substructure geometry in the form of top of bearing seat elevations is presented. Example problems are used to reinforce the information presented. Curved Bridge Geometry (T520) on May 28, 2019 at 2:00 PM Eastern time This course advances the approach to bridge geometry developed for straight bridges to curved bridges. The geometry of curved bridges using both straight, chorded girders and curved girders is presented. The geometry of two curved bridge types (precast segmental box girders and curved u-girders) is introduced and an approach to computing their geometry is outlined.

This material is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange under DTFH61-13-D-00010 Task No. 5010. The U.S. Government assumes no liability for the use of the information. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this material only because they are considered essential to the objective of the material. They are included for informational purposes only and are not intended to reflect a preference, approval, or endorsement of any one product or entity. All Photos: Corven Engineering Inc. Corven Photos: Engineering All PROJECT

Aerial view of a mainline Northwest bridge. Bridge 25 parallels existing southbound lanes and is over 1 mile long. Photo: Corridor Aerial Innovations of Express Lanes Georgia Inc.

by Alan Kite, Parsons Corporation

The Interstate 75/Interstate 575 parallel to I-75 to Hickory Grove Road (I-75/I-575) corridor northwest of (approximately 17 miles) and from the the Atlanta Beltway, or Interstate I-75/I-575 interchange parallel to I-575 285 (I-285), runs through a densely to Sixes Road (approximately 12 miles). Project location and vicinity map. Photo: populated and rapidly growing section The project scope included 39 bridges, Parsons. in the Atlanta, Ga., metropolitan area. two major interchanges, roadway, This corridor currently accommodates signing, tolling facilities, intelligent 297,000 vehicles per day, which transportation systems, and all ancillary almost meets the traffic projection of structures for the project. Flyover ramps 310,000 vehicles per day by 2035 per within the I-75/I-285 interchange are the project’s environmental assessment. up to 2827 ft long with span lengths Several planning studies over the past up to 175 ft and pier heights up to 90 15 years have looked for economical ft to cross numerous roadways, existing alternatives to alleviate daily traffic flyover ramps, and irregular terrain. congestion, increase traffic capacity, and provide a construction scheme Prestressed concrete girders were used with minimal impact on existing traffic. on several of the interchange bridges In the fall of 2013, a public-private to construct cost-effective and low- partnership, design-build-finance maintenance structures. North of the contract was executed to construct I-75/I-575 interchange, mainline viaduct reversible managed toll lanes that superstructures are 39.25 ft wide with will allow drivers to choose to pay a four prestressed concrete bulb-tee dynamically priced toll to bypass beams, 72 to 74 in. deep, supported congestion. on single-column hammerhead piers. Bridge lengths range from 1298 to The project extended from the I-285 5981 ft to span over existing local Project location and vicinity map. (Atlanta Beltway)/I-75 interchange roads, railroads, streams, wetlands, and All Figures: Parsons.

NORTHWEST CORRIDOR EXPRESS LANES / MARIETTA, GEORGIA profile BRIDGE DESIGN ENGINEER: Parsons, Peachtree Corners, Ga. OTHER BRIDGE CONSULTANT: Heath & Lineback Engineers, Marietta, Ga. PRIME CONTRACTOR: Northwest Express Roadbuilders, a joint venture of Archer Western and Hubbard Construction Company, Marietta, Ga. PRECASTER: Standard Concrete Products, Atlanta, Ga.—a PCI-certified producer POST-TENSIONING CONTRACTOR: Freyssinet Inc., Sterling, Va. OTHER MATERIAL SUPPLIERS: Mechanically stabilized earth wall panel fabricator: Reinforced Earth Company, Atlanta, Ga.; noise barrier panel fabricator: Oldcastle Precast Inc., Newnan, Ga.—a PCI-certified producer

16 | ASPIRE Spring 2019 on/off ramps to I-75. Throughout the with all offices were held to discuss project corridor, smaller bridges were design issues, the use of similar details, used to span over local roads and and adherence to the design schedules. streams. Precast Concrete Pier Caps The $654 million design-build-finance Numerous project challenges related project required a fast-paced design to site conditions and economical schedule, with all bridge and structure construction methods had to be design to be completed in 15 months. resolved at various locations along the To meet this schedule, design teams alignment. At one project location, a were established in six Parsons offices proposed 3500-ft-long bridge would (Atlanta, Ga.; Baltimore, Md.; Boston, be adjacent to the existing I-75 Mass.; Chicago, Ill.; Orlando, Fla.; and roadway. A mechanically stabilized Washington, D.C.) and the local office earth (MSE) wall supported the existing of Heath & Lineback Engineers to fill, with a stream and environmentally create the design and generate contract sensitive wetlands located at the documents. Each office was assigned bottom of the wall and running parallel bridges with similar superstructure to the interstate. Eighteen single- Cross section of a 3300-ft-long bridge and substructure types and similar column piers along the proposed adjacent and parallel to southbound span arrangements to provide design bridge were to be constructed in the Interstate 75, the existing retaining wall, consistency and an efficient design narrow wetlands area between the and wetlands. Figure: Parsons. that met the design schedule. Another stream and the wall. advantage of using multiple offices pressure behind the existing MSE wall. was that it allowed independent design During the early stages of the project, This system minimized the impact on the checks on major bridge elements to be it was evident that access to the site, environmentally sensitive wetlands area, performed by engineers not directly traffic maintenance, and minimizing remained within the required vertical and involved in the initial design. impact on the wetlands would be a lateral structural loading capacities, and major challenge. Two alternatives were limited traffic interruptions. Prior to the start of design, a project- evaluated: building a conventional specific design criterion was written temporary work bridge, and using Precast concrete caps were cast by that included contract-specific accelerated bridge construction methods the contractor at a yard located requirements, Georgia Department of with precast concrete pier elements. approximately 5 miles from the pier Transportation (GDOT) bridge standards, Ultimately, it was decided to perform all construction site. The precast concrete and contractor-preferred materials (for major construction activities from the units were transported individually example, concrete strengths), where existing southbound interstate shoulder using a single specialized-permit vehicle. applicable. with limited nighttime lane closures. A rapid setup/takedown type of crane was used to erect the precast concrete Precast concrete girders were selected The piers are founded on 78-in.-diameter caps onto a temporary support bracket because rapid construction was critical drilled monoshafts. Excavated spoil was attached to the top of the column. The to meeting the schedule, and because contained with permanent casings that temporary shoring bracket included of their additional benefits of high were installed with drilling equipment screw jacks mounted on top of the pier durability, low maintenance, excellent staged on the southbound I-75 shoulder. column to support and provide geometry quality, and low cost relative to other The maximum offset from the existing control to the precast concrete cap construction materials. In addition, I-75 southbound curb to the centerline before the connection was cast. standard details were established and of the pier shaft was limited to 7.5 ft. provided to each bridge design team to This distance was dictated by the A cast-in-place concrete bedding ensure project-wide design and detailing practical reach of the drilling rig as well layer between the top of column and consistencies. Weekly conference calls as the maximum allowable surcharge bottom of cap was used to provide

GEORGIA DEPARTMENT OF TRANSPORTATION, OWNER BRIDGE DESCRIPTION: The project included 39 bridges; mainline bridges were between 807 and 5981 ft long and 29 ft 3 in. to 39 ft 3 in. wide. Mainline bridge superstructures have a 7½ in. thick cast-in-place concrete deck and prestressed concrete girders. STRUCTURAL COMPONENTS: Mainline bridges used BT72 and BT74 prestressed concrete bulb-tee girders supported on single-column hammerhead piers and drilled shafts or piles; precast concrete pier caps; and precast concrete post-tensioned straddle-beam piers BRIDGE CONSTRUCTION COST: $131 million AWARDS: 2018 Roads & Bridges #1 Road; Georgia Engineering Excellence Award Winner in Transportation; Georgia Partnership for Transportation Quality Preconstruction Design Award Grand Prize Winner; Precast Concrete Institute 2019 Design Award Main Span More than 150 Feet

ASPIRE Spring 2019 | 17 Erection of a precast concrete pier cap Lifting the post-tensioned precast concrete portion of a straddle bent cap from the fill from the adjacent Interstate 75 shoulder. embankment. The top of the embankment was constructed at the same slope as the Photo: Northwest Express Roadbuilders. final cap geometry to control the geometry of the formwork and post-tensioning ducts. The bottom segment of the cap was cast on the ground and lifted into place after post- tensioning. The top portion of the cap was then cast in place. Photo: Northwest Express Roadbuilders. construction tolerance and to position the bridge, three types of intermediate design strength) before tensioning. the precast concrete cap. The cap- piers were used: conventional The “U” shape also minimized the column connection was established hammerhead on a single column, lifting weight (210 kip) and provided using a filleted rectangular blockout inverted-tee hammerhead on a single part of the formwork for the cast- (with 7.375 in. chamfers at each column, and inverted-tee straddle in-place concrete after the precast corner) in the precast concrete cap. bent on two columns. The inverted- concrete member was erected on the Headed dowels, confined by heavy tee hammerhead pier caps were used columns. The prestressed beam seats transverse reinforcement, reinforced the in two of the intermediate bents to were constructed as part of the precast connection zone. mitigate the limitations on the available concrete section, with 2-ft 2-in.-wide vertical clearance under the bridge. ledges on each side of the 5-ft-wide The precast concrete cap reinforcement core precast concrete section. During was detailed to avoid conflict with A straddle bent was selected primarily a temporary nighttime (11:00 p.m. to the headed dowels. The size and because of the sharp skew angle and to 4:00 a.m.) shutdown of the existing reinforcement detailing of the keep the maximum span lengths around southbound I-75, traffic was detoured connection were designed to utilize 150 ft, which would make the best use to adjacent roadways and I-285. During f standard strength concrete ( ’c = 4.5 of precast concrete girders. The location this time, two 300-metric-ton mobile ksi). Constructing the pier column from of the straddle bent was chosen to hydraulic cranes were used to lift the the I-75 shoulder and using precast minimize its length and to balance loads cap and place it on top of the columns. concrete elements efficiently minimized from the adjacent spans. The formwork for the cast-in-place both traffic disruptions and the portion of the bent cap was then lifted environmental impact of the project. To make the straddle bent, a fill and connected to the precast concrete embankment with the same slope as section. The cast-in-place concrete was Precast, Post-Tensioned the final slope of the precast concrete placed later with protection measures Straddle Bent Caps bent cap was constructed; this in place while traffic was maintained At a second site, an 806.5-ft-long, facilitated geometric control of the below. six-span bridge carries the I-75 formwork and the post-tensioning express roadway over the existing ducts. The precast concrete bent cap The cast-in-place portion of the bent cap I-75 southbound lanes. The roadway’s was cast on site, adjacent to the final reached a minimum strength of 5 ksi horizontal alignment at the bridge bent location, and post-tensioned and before the prestressed concrete girders is highly skewed with respect to the grouted while on the ground. The were erected. To maintain structural roadway below and consists of two precast concrete cross section was a stability of the precast concrete section reverse curves with a short tangent “U” shape to allow for seven ducts, after erection on the columns, the top of between the curves. The overall width each with nineteen 0.6-in.-diameter the 5-ft-wide column was flared to 8 ft 6 of the bridge varies from 29 ft 3 in. to strands tensioned in a single-stage post- in. wide in the longitudinal direction. The 35 ft 3 in. tensioning operation. The concrete for precast concrete cap width was similarly the cap was at least 14 days old and flared to 8 ft 6 in. to accommodate two Given these geometric constraints and had reached a compressive strength bearings at each column. the presence of existing roadways under of 7 ksi (which was also the 28-day

18 | ASPIRE Spring 2019 Cross section of a straddle bent cap. The shaded area is the precast concrete section with seven post-tensioning ducts and Conclusion longitudinal girder bearing seats. The cast- The Northwest Corridor Express Lanes in-place concrete portion of the section was opened to traffic in September 2018 placed after cap erection and over traffic. after 5 years of design and construction. During the first month of operation, more than 20,000 vehicles per day were using the express lanes, far exceeding initial projections. The 29.7-mile-long corridor is the longest installation in the Georgia express lane system and has received glowing reviews from the traveling public and GDOT, which noted that the project has set the bar for future mega-design-build project delivery within Georgia and around the country. TYPICAL SECTION OF STRADDLE BENT SECTION AT COLUMN ______PRECAST CONCRETE PRECAST CONCRETE Alan Kite is a senior project manager with Parsons Corporation in Baltimore, Md., and was the lead structural engineer for the Northwest Corridor Express Lanes project.

A straddle bent with flared ends to support two bearings at each end of the pier cap. Photo: Parsons.

WATER RESOURCES Concrete I Roller Compacted Concrete I Soil-Cement DAMS OVERTOPPING PROTECTION FLOOD CONTROL EMBANKMENT PROTECTION WATER SUPPLY LINERS

www.cement.org/water

ASPIRE Spring 2019 | 19 PROJECT The Brotherhood Bridge over the Mendenhall River

by Elmer Marx, Alaska Department of Transportation and Public Facilities

Temporary work trestle. All Photos and Figures: Alaska Department of Transportation and Public Facilities.

The Brotherhood Bridge (also known as girder structure, was built and named the requirements became more stringent, the Mendenhall River Bridge) is located “Brotherhood Bridge” to commemorate the need for a replacement bridge near Juneau, Alaska, about five miles the 50th anniversary of the Alaska Native became apparent. Construction of the downstream of the Mendenhall Glacier. Brotherhood (ANB). replacement bridge began in April 2014. The project, which has interesting The new bridge, which was rededicated historical connections to the region’s Roy Peratrovich Jr. was an engineer for in October 2015, retains the name and Native Alaska community, faced several the Alaska Department of Highways decorative bronze medallions that are a unique design challenges not often team that designed the 1965 key part of the Brotherhood spirit. encountered outside of Alaska and structure. He is a Tlingit of the Raven incorporates many features commonly Lukaax.ádi clan, the first Alaska Native Geological and used by the Alaska Department of person registered as a professional Hydrological Considerations Transportation and Public Facilities civil engineer in Alaska, and the son The Mendenhall Glacier is viewed (AKDOT&PF). of prominent Alaska Native civil rights by more than 500,000 tourists every leaders Elizabeth and Roy Peratrovich year. Currently, the face of the glacier History Sr. In honor of the ANB anniversary, is located about 1.5 miles from the Five bridges have been built to cross the Peratrovich Jr. sculpted 10 bronze Mendenhall Glacier Visitor Center; Mendenhall River at this location. The first medallions with the ANB crest and however, several hundred years ago, the road crossing at the river, a timber trestle, imagery, which were incorporated into face of the glacier was located near the was constructed in 1903 for a total the bridge rail of the 1965 structure. bridge site. As the glacier has retreated, cost of $1700. The timber trestle was the surrounding ground surface has reconstructed in 1919 and then replaced The bridge served the community risen due to isostatic glacial rebound. At with a single-lane, two-span steel truss well for about five decades. But, as the bridge’s location, the ground surface in 1931. In 1965, the fourth bridge, a the weight of trucks increased, traffic is rising at a rate of about 1 in. per year. two-lane, three-span continuous steel demands grew, and design code Consequently, the river is incising and

BROTHERHOOD BRIDGE (MENDENHALL RIVER BRIDGE) / JUNEAU, ALASKA profile BRIDGE DESIGN ENGINEER: Alaska Department of Transportation and Public Facilities Bridge Section, Juneau PRIME CONTRACTOR: Orion Marine Group, Anchorage, Alaska PRECASTER: Concrete Technology Corporation, Tacoma, Wash.—a PCI-certified producer GEOTECHNICAL AND FOUNDATION CONSULTANTS: Jacobs (formerly CH2M Hill), Bellevue, Wash. OTHER MATERIAL SUPPLIERS: Formliner (enlarged version of medallions): Spec Formliners Inc., Santa Ana, Calif.; elastomeric bearing pads: Seismic Energy Products LP, Athens, Tex.

20 | ASPIRE Spring 2019 pier scour, isostatic glacial rebound, triggered at depths in excess of 100 and jökulhlaups undermined the pier ft and might result in free-field lateral footings of the previous bridge and spreading of between 4 and 6 ft at were among the contributing factors for bridge abutments and center piers. At why it had to be replaced. this level of deformation, the bridge could not be guaranteed to satisfy the Geotechnical and American Association of State Highway Seismic Considerations and Transportation Officials (AASHTO) Much of Alaska’s coastline is located on requirements for noncollapse. Therefore, Ten bronze medallions from the 1965 the Pacific “Ring of Fire.” Consequently, some form of liquefaction mitigation bridge commemorating the 50th Alaska is subjected to frequent and was required. anniversary of the Alaska Native strong ground shaking. Although the Brotherhood were reused in the seismic hazard at the bridge site (peak ADOT&PF worked with CH2M Hill (now new bridge railing. The sculptor, Roy ground acceleration ~0.2g for the 7% Jacobs) to examine various approaches Peratrovich Jr., was a member of the probability of exceedance in the 75-year to address the seismic demands at the Alaska Department of Highways team design event) is not particularly large site. Pseudostatic slope stability analyses that designed the 1965 structure. He was compared to other places in Alaska, it using limit equilibrium methods were the first Alaska Native person registered was predicted to be enough to generate conducted to evaluate the seismic as a professional civil engineer in Alaska. soil liquefaction below the bridge. stability of the abutment during and lowering the streambed surface below immediately after the design seismic the bridge—that is, the exposed length Geology at the bridge site is composed event. of the piers will increase over the life of of over 150 ft of nonplastic silts and the bridge. This phenomenon had to be sands. Blow counts from standard The response was evaluated for two considered when planning for pier scour penetration tests within the silts and conditions. The first considered flow over the design life of the structure. sands were generally under 15 blows failure. In this case, the soil liquifies and per foot; cone penetrometer test loses strength when the ground is not The recession of the Mendenhall Glacier soundings and shear wave velocity shaking. This case has been observed has resulted in several unusual flood- measurements confirmed very soft to when liquefaction is slow to develop, like events that have followed the loose soil conditions. sometimes occurring several minutes outbursts of glacier-dammed lakes. Such after the end of the earthquake. The events are known by the Icelandic term Preliminary analyses showed that second condition considered lateral jökulhlaups (pronounced “yo-KOOL- sediment liquefaction could be spreading, where reduction in soil lahps”). The Mendenhall River Installing the precast, prestressed concrete decked bulb-tee girders during nighttime jökulhlaups have caused floodwater construction. During the summer in Alaska, there is still daylight or twilight during surface elevations above those of the “nighttime” construction. 50-year flood event and accelerated erosion along the riverbanks (which are partially lined by residential structures). Predicting these events can be difficult given the uncertainties of lake volumes, fill rates, glacier buoyancy, and other contributing factors. In addition to the transport of large wood debris, jökulhlaup floodwaters may include large chunks of ice.

The previous bridge substructure was founded on driven steel H-piles that penetrated up to 70 ft beneath the streambed. The effects of local

ALASKA DEPARTMENT OF TRANSPORTATION AND PUBLIC FACILITIES, OWNER BRIDGE DESCRIPTION: Three-span, prestressed concrete decked bulb-tee girder superstructure on reinforced-concrete-filled steel pipe pile extension bents STRUCTURAL COMPONENTS: Forty-two 65-in.-deep decked bulb-tee girders; twenty-eight 2-ft-diameter reinforced-concrete-filled steel pipe piles at the abutments; ten 4-ft-diameter reinforced-concrete-filled steel pipe piles at the piers; cast-in-place concrete pile caps, diaphragms, traffic barriers, and approach slabs BRIDGE CONSTRUCTION COST: $11 million ($294/ft2) AWARD: Outstanding Project of the Year Award, American Society of Civil Engineers, Alaska Section, Juneau Branch

ASPIRE Spring 2019 | 21 strength and ground shaking occur in combination. These analyses were performed without consideration of the “pinning” effects from the abutment or pier piles. Both circular and noncircular failure surfaces were evaluated.

Once the “free field” condition had been better quantified, the option of pile pinning was examined. In the pile- pinning approach, restraint is provided by the bridge superstructure (acting as a strut) and by the lateral resistance of reinforced-concrete-filled steel pipe piles displaced during slope movement, which results in stabilizing forces to slope movement. This approach provided bridge stability without the need for expensive ground improvement work. Typical section of the precast, prestressed concrete decked bulb-tee girder superstructure Preliminary assessments found that that is supported on reinforced-concrete-filled steel pipe pile extension bents. the depth and location of ground improvement would cost over $2 predecked girder cross sections can of 10 to 12 ksi. This high-strength, million. Given the costs, environmental be constructed rapidly, an important high-durability concrete is used in the constraints, and schedule limitations, pile consideration given Alaska’s cold climate entire concrete section, including the pinning was evaluated to provide a cost- and short construction season. The monolithic deck. The three precast effective approach for the liquefaction girders were fabricated at Concrete producers that provide decked girders hazard. The use of pile pinning has Technology Corporation’s Tacoma, for projects in Alaska (two in Anchorage, become a frequent approach for other Wash., facility. This facility is located Alaska, and one in Tacoma, Wash.) have AKDOT&PF bridge projects. on a maritime waterway and has direct the capability to deflect (sag) the forms access from the fabrication floor to an downward to offset prestress camber Design and Construction awaiting barge. All 42 girders were as a method to achieve the roadway The Brotherhood Bridge is located shipped on one barge. The barge profile grade needed for the roadway near a popular pedestrian trailhead arrived at the Juneau dock where the surface. Leveling inserts are provided and area for viewing/photographing girders were loaded on trucks and in the girders to provide a method of the Mendenhall Glacier. The new driven approximately ten miles to the adjusting differential camber between three-span structure is 378 ft long, bridge location. In Alaska, girders up girders, if needed. High-strength (9 with two lanes in each direction and a to 165,000 pounds are commonly ksi) grout is used in the longitudinal center turn lane. In addition to traffic, transported in this manner. keyways between the girders. The the bridge also carries water, electric, combination of using the zero-tension and telecommunication utilities. It AKDOT&PF designs these sections stress limit for design and high concrete has 8-ft-wide shoulders, a 6-ft-wide to a zero-tension stress limit with strength has resulted in a very durable, sidewalk on the downstream edge of the AASHTO LRFD Service III load nearly maintenance-free superstructure the bridge, and a 14-ft-wide multiuse combination using gross-section that is well suited to Alaska’s severe pedestrian pathway on the upstream properties. The specified 28-day concrete environment. edge for a total bridge width of 99.5 ft. compressive strength of these sections is typically a minimum of 7.5 ksi, with For several decades, AKDOT&PF has Steel and concrete options of various fabricators commonly achieving strengths used reinforced-concrete-filled steel span configurations were considered Completed first-stage pier using reinforced-concrete-filled steel pipe piles with for the replacement bridge. Ultimately, reinforcement extended from top of cap to engage the diaphragm between girders. a three-span, precast, prestressed concrete decked bulb-tee girder superstructure supported on reinforced- concrete-filled steel-pipe-pile extension bents was found to be the most cost- effective solution for the site.

Precast, prestressed concrete decked bulb-tee girders have been used in Alaska since the mid-1970s. In addition to being more durable than bridges with cast-in-place decks, bridges with

22 | ASPIRE Spring 2019 Brotherhood Bridge to allow pedestrians evaluation of the seismic response and bicyclists to safely cross under of both stages, to ensure safe and the highway along the riverbanks. adequate performance during the entire Mechanically stabilized earth walls are construction process. utilized at each abutment to improve pedestrian access under the bridge. During construction of the bridge, The bridge abutments are supported a jökulhlaup occurred, carrying by fourteen 2-ft-diameter concrete- large amounts of wood and debris. filled pipe piles under each cap beam Fortunately, the bridge contractor to accommodate the large seismic was able to quickly respond to the demands, including predicted pile- unexpected event and removed debris pinning action and lateral soil movement. around the work trestle during the outburst and for several days after it. Above the bedrock at the site was 290 ft of very loose soils. Based on the The deck and cast-in-place approach Aerial view of the bridge with the first two-dimensional, site-specific seismic slabs are covered with a waterproofing stage of construction nearly complete; analysis, the five 48-in.-diameter pipe membrane and 4 in. of asphalt the work trestle is on the left, and the piles driven to bedrock and partially concrete. Concrete formliner replicas old bridge is on the right. filled with concrete were found to be of the ANB medallions were fabricated the most cost-effective foundation and used in the wingwalls. Cast-in-place pipe pile extension substructures type for the bridge piers. Only the top end, pier, and intermediate diaphragms (piles typically range from 2 to 4 ft in 85 ft of the pipe piles are filled with are used in the superstructure. The diameter for conventional bridges). reinforced concrete. The design required abutments employ a semi-integral Because this type of substructure does concrete to be placed below the ground abutment concept that results in a not require cofferdams, it can be built line to a point where the moment is less jointless bridge and subsequently in less time than more traditional, pile- than half the maximum plastic hinging reduced maintenance needs. supported footings. The steel pipe moment accounting for the effects of acts as a stay-in-place form for the scour, liquefaction, and other factors The total cost of the project, including reinforced-concrete core and is included that lower the plastic hinge location. demolition of the existing bridge, in the cross-sectional capacity of the was approximately $11 million, which members. The upper lengths of the Because the AKDOT&PF right-of-way is corresponds to about $294 per square pipe (exposed length and 10 ft below relatively narrow at this crossing, staged foot of bridge deck area. Conventional the minimum streambed surface) are half-width construction was selected to highway bridges in Alaska typically cost hot-dip galvanized. AKDOT&PF requires allow traffic during construction. About between $300 and $350 per square the use of steel pipes that comply with one-third of the new bridge was built foot. Considering the use of staged either the American Petroleum Institute upstream of the old steel girder bridge construction, decorative railing, long (API) 5L PSL2 X52 or ASTM A709 Grade without affecting traffic. Once the first piles, and poor soil conditions, the 50T3 fabricated to API 2B or AKDOT&PF stage of construction was complete, Brotherhood Bridge proved to be a spiral (helical) weld specifications to vehicular and pedestrian traffic was very cost-effective structure. The high- provide superior seismic performance. routed over the new bridge. The old strength precast concrete decked bulb- Research performed at bridge was demolished, and the steel tee girders will provide a durable bridge State University developed strain limits was sent to a recycling facility outside of requiring minimal maintenance over the of reinforced-concrete-filled steel tubes Alaska. The rest of the new bridge was structure’s design life. (RCFSTs) associated with the onset of constructed and traffic was placed in ______pipe wall buckling and fracture (for the final configuration. more information, see the Concrete Elmer Marx is a senior bridge design Bridge Technology article on RCFSTs Since construction was staged, full engineer with the Alaska Department in this issue of ASPIRE® on page 32). designs were completed for the two of Transportation and Public Facilities in These composite concrete-steel sections bridge configurations, including Juneau. are stiffer, stronger, and more ductile than conventional reinforced concrete or hollow steel members and are better able to accommodate large lateral demands from ice, earthquakes, and vehicle collisions.

The project included construction of paths below both sides of the

Aerial view of the bridge carrying traffic while the second stage of construction was underway. PROJECT Sarah Mildred Long Bridge The movable midspan, elevated clearance, and reduced number of piers of this replacement bridge over the Piscataqua River improve marine navigation

by Jeffrey S. Folsom, Maine Department of Transportation

Built in 1940, the original Maine– design would have made her proud. for vehicles, rail lines, and maritime New Hampshire Bridge spanning the The previous structure had five main vessels. With the new bridge, maritime Piscataqua River between Portsmouth, truss spans, including the vertical lift vessels can navigate the Piscataqua N.H., and Kittery, Me., served as the span, along with 15 roadway spans on River while the upper segmental- critical backup route between Maine the Portsmouth side and seven on the approach superstructure carries U.S. and New Hampshire if traffic were Kittery side. The new Sarah Mildred Route 1A (Bypass) and the lower disrupted on the Interstate 95 Bridge Long Bridge has twin segmental- segmental superstructure connects upstream. In 1987, the Maine–New concrete approach spans in a stacked Pan Am Railways, a railroad system for Hampshire Bridge was renamed to configuration leading to a single-deck the Northeastern United States, to the honor Sarah Mildred Long, an employee hybrid movable span at its center. Portsmouth Naval Shipyard. The movable of the Maine–New Hampshire Interstate hybrid span rises to allow passage of Bridge Authority for 50 years. The new structure’s design, which tall vessels and lowers to railroad-track provides a unique concept for a level for trains to cross, remaining at Three decades later, on March 30, segmental bridge, improves the skew the vehicle level in its resting position. 2018, a replacement bridge, also angle and width of the navigation The Portsmouth, Me., approach spans named for Long, opened. Its innovative span as well as safety and efficiency extend over Market Street and the Pan

The new Sarah Mildred Long Bridge between Maine and New Hampshire over the Piscataqua River features twin segmental- concrete approach spans in a stacked configuration leading to a single-deck, hybrid movable span at the bridge’s center. Photo: FIGG Engineering Group.

SARAH MILDRED LONG BRIDGE / PORTSMOUTH, NEW HAMPSHIRE, AND KITTERY, profile MAINE BRIDGE DESIGN ENGINEERS: FIGG Bridge Engineers, Tallahassee, Fla., and Hardesty & Hanover, New York, N.Y., a joint venture PRIME CONTRACTOR: Cianbro, Pittsfield, Me. POST-TENSIONING CONTRACTORS: GZA GeoEnvironmental, Boston, Mass.; Sebago Technics, Portland, Me.

24 | ASPIRE Spring 2019 Am Railways’ Newington Branch railroad The new bridge was designed by a traffic could pass. In 2008, the bridge tracks. The Kittery approach spans cross joint venture of the specialty bridge opened 2637 times, with an average Bridge Street. design firms FIGG Bridge Engineers traffic delay of 9.5 minutes per opening. and Hardesty & Hanover, and it was The new bridge offers 56 ft of vertical Selection of a segmental concrete solution delivered through a new construction clearance in its resting position. As a helped project leaders achieve many of manager/general contractor method, in result of the increased vertical clearance, their goals for the bridge. It allowed them which a construction manager (Cianbro 68% fewer openings will be required to fine-tune both horizontal and vertical Corporation), chosen through an RFP with the new structure. The bridge can alignments to improve the navigation process, was an active participant in the remain at its resting position, the vehicle span, meeting geometric standards design process. level, almost all of time because only 10 related to both railroad and vehicular trains typically use the lower-level tracks traffic, and it minimized the impact of Design work began in late 2012. Early each year. the project on the environment, historic on, Cianbro provided constructability and archaeological sites, and nearby reviews and input on scheduling The previous bridge provided only 175 properties. The use of concrete also parameters, cost elements, and ft of useable width for maritime traffic, offered a context-sensitive, aesthetically other factors. The goal was for the forcing tugboats to disengage from pleasing solution. construction manager to provide a larger ships before passing through the reality check on the constructability and span. To improve accessibility for ships Throughout the design process, the team economy of the design as it evolved. approaching the open span, a new gained insight from extensive public alignment was created that provides involvement and government agency When Cianbro became construction a 15-degree skewed crossing to the outreach to the community, regulatory manager, the owners and Cianbro bridge (the original crossing skew was interests, and ship pilots. This input helped negotiated a construction contract, 25 degrees). The alignment change guide designers and contractors to a with the intent that if they could agree increases useable width to 250 ft. design that meets all of the project goals on a price, Cianbro would also be the while creating a striking design with a general contractor. If no agreement To improve unique lift concept that can serve as a were reached, the owners would template for future projects of this type. advertise for competitive bids. Cianbro accessibility for ships Details of the design and construction of prepared cost estimates at 30%, 60%, approaching the open the lift tower foundation can be found in and 100% design plan reviews. The a Concrete Bridge Technology article on estimate prepared at 100% was the span, a new alignment page 34 of this issue. basis of negotiation. The final pricing was created that and negotiations resulted in a few plan Project Partners, and specification changes that were provides a 15-degree Funding, and Vendors incorporated into one final released- skewed crossing to the The replacement bridge project was a for-construction set of contract partnership among the Federal Highway documents. It was at that point that a bridge. Administration, the Maine Department construction contract was signed and The larger opening was achieved with a of Transportation (MaineDOT), and Cianbro became the general contractor. 4770 ft reverse curve on the approach the New Hampshire Department of Construction commenced in late 2014. bridge on the New Hampshire side and Transportation, with MaineDOT serving a 5200 ft radius curve on the Maine side, as the lead agency. Funding for the $165 Improving Maritime which connects back into the existing million project was aided by a $25 million Clearance and Accessibility alignment. This design allows the next Transportation Investment Generating Clearance and accessibility for maritime generation of cargo vessels to pass Economic Recovery (TIGER) grant for the vessels were among the primary through the span with tugboats engaged. railway portions. The project was the concerns tackled by the design team. second in a “Three Bridge Agreement” The original bridge offered just 10 ft Span Design between Maine and New Hampshire of clearance in the closed position, The new bridge features 11 upper to address their jointly owned bridges which meant that bridge openings vehicle spans: 160-270-270-320-320-35 spanning the Piscataqua River. were frequently required so maritime (tower span)-300 (lift span)-35 (tower

MAINE DEPARTMENT OF TRANSPORTATION AND NEW HAMPSHIRE DEPARTMENT OF TRANSPORTATION, OWNERS BRIDGE DESCRIPTION: 1990-ft-long bridge with twin segmental-concrete approach spans in a stacked configuration leading to a single-deck, hybrid movable span at the bridge’s center. The lift span is supported by four 200-ft-high precast concrete towers at the span’s corners. STRUCTURAL COMPONENTS: 229 precast concrete segments in 11 upper vehicle spans: 160-270-270-320-320-35 (tower span)-300 (lift span)- 35 (tower span)-200-320-200 ft; and 126 precast concrete segments in 16 lower railway spans: 60-100-160-160-160-160-135-65-35 (tower span)-300 (lift span)-35 (tower span)-65-135-160-160-100 ft. Each tower consists of 21 precast concrete match-cast segments. BRIDGE CONSTRUCTION COST: $165 million AWARDS: 2018 International Bridge Conference Special Award of Merit; 2018 Roads and Bridges Magazine Top Ten Bridges

ASPIRE Spring 2019 | 25 A ship passing through the movable span A new alignment was created for The upper vehicular spans feature during construction shows the added the replacement bridge, reducing precast concrete segmental box girders width for maritime traffic and the size the crossing skew to 15 degrees for with depths varying between 8 and 13.5 of ship that needs to be accommodated. approaching ships. Photo: Maine ft and base widths varying from 15 to Photo: Maine Department of Department of Transportation. 16.75 ft. Photo: Maine Department of Transportation. Transportation.

span)-200-320-200 ft. The lower railway lengths. As a result, 11 fewer piers 5-ft 7-in.-wide median that contains the level consists of 16 spans: 60-100-160- were needed in the waterway, and railroad tracks. 160-160-160-135-65-35 (tower span)- an existing median pier on Market 300 (lift span)-35 (tower span)-65-135- Street was eliminated, improving the Modified Tower 160-160-100 ft. Many of the railway gateway span leading into downtown Drive System level’s span lengths are approximately Portsmouth. Several options were considered for half the length of the vehicle level to the drive system to operate the accommodate the heavier (Cooper The upper vehicular spans feature central 300-ft-long streamlined box- E80) required live load. The goal was precast concrete segmental box girders girder lift span. Typically, two options to maximize span lengths on each level with depths varying between 8 and are available. With a span drive, the to reduce the number of piers in the 13.5 ft and base widths varying from machinery is located on the span, waterway. 15 to 16.75 ft. The lower railway spans raising and lowering itself with consist of precast concrete segmental the span. With a tower drive, the The 160 ft length for the railway spans girders varying in height from 9 to 11 machinery, located at the tops of the is significant for a segmental bridge ft, with top flanges of 19 ft and base towers, raises or lowers the span. For and allowed for only an intermediate widths varying from 11.33 to 12 ft. The this project, a hybrid design provided monoshaft pier to be used at the single-level lift-span deck is 42 ft 7 in. the best of both worlds. midspans of the upper level’s 320 ft wide, with two lanes separated by a The operating equipment is located at the base of the four 200-ft-tall precast concrete towers, on each corner of the span. The machinery was placed at the bases, providing easy access for maintenance and inspection. Similar to a span drive, the equipment uses uphaul and downhaul ropes to physically pull the span up and down and does not rely on the friction of the counterweight sheave to move the span. As with a tower drive, the equipment is enclosed within the towers, including mechanicals, wiring, and even the maintenance stairway. The counterweights were built with steel plates inside a steel box. Steel was selected after evaluating it against other options, such as lead, to determine the cost-benefit ratios and compare densities to the total heights of the materials that would be needed. The towers feature glass windows that provide ambient lighting for maintenance crews and also allow drivers to see the counterweights moving when the span is raised and Each lift tower consists of 21 precast concrete segments cast at the project site using lowered. match-casting procedures. Photo: Maine Department of Transportation. The lift span features guide rollers that

26 | ASPIRE Spring 2019 run on plates attached to the towers to segments were cast at the project site maintain the transverse and longitudinal using standard segmental concrete position of the span as it is raised and match-casting procedures. Forms were lowered. The span joins at the primary stripped from wet-cast segments and CALLFOR (vehicle) resting level with a standard moved into place to serve as a match-cast ENTRIES finger joint. Openings allow the tower segment. After the first three segments rails to pass through the span and were erected and adjusted to the proper continue down to the railroad level. line and grade, a 3 ft starter segment At that point, a plate with mitered was cast below to establish the baseline rails connects to the tracks. It was erection geometry. This was necessary to challenging to detail this configuration begin erection of the tower segments. because joints usually are not designed The match-cast precast concrete tower to have tracks pass through them and segments needed to be placed on top of continue below. the cast-in-place footing. To ensure the correct starting geometry, the segments Cost Efficiency of Precast were erected on temporary supports and Concrete Towers properly adjusted, with a short closure Precast concrete was chosen for the pour between the precast concrete tower towers after all possibilities were segments and the cast-in-place footing. evaluated. This option was most Erection geometry was monitored efficient and cost effective because all and adjusted as necessary to maintain The the equipment and setup needed for erection tolerances. The towers were erection, post-tensioning, and epoxy capped with a precast concrete tower cap joining for the tower segments were with cast-in-place concrete topping. already on site for the precast concrete ______segmental superstructure. Jeffrey S. Folsom, P.E., is assistant bridge program manager with the Each tower consists of 21 precast Maine Department of Transportation in concrete match-cast segments. Tower Augusta. 57th AnnuAl PCI DesIgn AwArDs The Sarah Mildred Long Bridge is an impressive eliminated the usual cross bracing and concealed bridge that meets a set of complex functional re- the lifting equipment. At the same time, the quirements while achieving a high level of visual haunched girders, which are deeper at the piers The 57th Annual PCI Design quality suitable for its location within an area that where the forces are the greatest, and the solid Awards will open for entries encompasses two historic cities and an attractive towers, rising from a massive base, provide an on May 20, 2019. Join us in our natural setting. Meeting both the functional and impression of great strength. This impression is aesthetic requirements of the project within a reinforced by the simple but robust modulation search for excellence and submit reasonable budget required innovation in layout, of the concrete piers. your projects electronically design, contracting arrangements, and construc- by August 19, 2019. tion. That the design, construction, and client There is also a kind of delicacy at the tops of the team was able to meet all of these requirements towers, which taper to reveal the counterweight so successfully is a credit to all involved. sheaves. Because the sheaves are a visual feature, the design conveys that the bridge is meant to Projects with this kind of functional complexity move. The sheaves are round, and things that are Visit PCi.org often have a corresponding and unattractive round rotate. Why else would they rotate but to visual complexity. The old bridge was an for more InformAtIon lift the center span? Finally, the vertical strips of AnD submIssIon DetAIls. example of that type of design. On the new tower windows that show the counterweights bridge, concrete segmental construction offered moving are visual compensation to drivers stuck in a solution to the aesthetic challenges. On the the traffic backup as a ship or train passes through spans, it allowed for fewer piers and simplified the crossing. Sarah Mildred Long would indeed be the appearance of the girders. On the towers, it proud of the bridge bearing her name. CONCRETE BRIDGE TECHNOLOGY Observations from 30 Years of Inspecting Post-Tensioned Structures

by Bruce Osborn, Structural Technologies LLC/VSL

During the 1970s, the construction of post-tensioned (PT) concrete structures rose in popularity as the technology allowed for the efficient construction of longer spans with smaller concrete sections and less mild-steel reinforcement. While this technological advancement has provided contractors and owners with a durable and cost- effective solution, it has not been without its challenges.

Since their inception, post-tensioning technology and specifications for PT bridges have evolved to ensure that long- lasting structures are being built with higher-quality installation procedures. Early failures of PT systems such as the Niles Channel Bridge (1999), Sunshine Skyway Bridge (2002), Varina-Enon Bridge (2007), and Mid-Bay Bridge (2011) pushed owners to implement closer inspection of PT systems. Figure 1. Bare strand in a tendon at a grout void. All Figures: Bruce Osborn. The following article shares the author’s Unforeseen Challenges caused excessive bleeding in the tendons. firsthand accounts of inspections of over In the early years of post-tensioning, The presence of bleed water increased the 70 bridges and approximately 18,500 stressing was regarded to be the most risk of voids during the grouting process, tendons. The author has inspected PT important aspect of the operation, thereby making the strands vulnerable to structures in some of the most benign and other details were believed to not corrosion. Voids discovered in this time and harshest environments from Alaska be as structurally significant. Even period were typically credited to excessive to Puerto Rico, and in many locations though grouting served as another layer bleed water, improper venting, poor in between. The condition of each PT of protection against corrosion of the grouting practices, or inadequate grout bridge was determined through analysis PT strands, it was often treated as an materials. of data gathered from destructive and afterthought and performed with limited nondestructive investigations performed supervision or inspection from an outside Notably, when inspections identified voids on external and internal post-tensioning party. Because the construction and in the grout within tendons, those voids systems. In the former type of system, inspection standards of past decades do were not always associated with significant tendons run within the void in box not meet today’s requirements, inspection corrosion. In most cases, voided areas girders or cable-stayed bridges; in the of older PT structures is important. could be regrouted to extend the service latter type, ducts for tendons are cast life of the structure and the PT system within the structural concrete section. Prior to 2000, grout used for tendons was within it. Figure 1 shows a borescope The findings illustrate the evolution of a simple mixture of Type I or II cement picture taken from the inside of a voided PT structures since the 1970s, common and water. In some cases, additives were tendon in a structure whose exterior types of deficiencies, and how shifts used to try to improve the protective condition was well maintained. The void is in quality-control procedures have characteristics of the grout. In later located at the top of the duct, and the steel improved installation and extended the years, it was proven that this combination within the tendon has not undergone any life of PT structures. of materials had segregation issues that major corrosion. This type of void is most

28 | ASPIRE Spring 2019 often caused when improper grout venting PT system itself. Cracks, which occur results in air entrapment at a high point. throughout the life of the structure, can To repair this type of condition, grout accelerate the intrusion of environmental ports are drilled into the duct and vacuum risks to the PT system. Environmental grouting is used to ensure a proper seal. conditions or the general upkeep of the When there is seemingly no corrosion, this structure surrounding the PT tendons, manner of repair is very beneficial. and not the PT tendons themselves, were typically the root cause. Tendons that are Of the bridges inspected, tendon sealed performed much better. deterioration could typically be attributed to severe cracking of the Figures 3 and 4 show two photos from deck surface at pier locations, which a structure in which large amounts of allowed contaminants to enter the water collected in the PT ducts. It was metal duct and access the grout and not known how the water was infiltrating tendon. As water entered the duct, it the system, but there were fears that the often traveled the length of the tendon PT system was at fault. As part of the in a process known as “wicking”; this investigation, ports were installed into same process can also occur in the seam the ducts, which were then pressurized, Figure 2. Bare strand with clear signs of of a metal duct. Figure 2 shows an to seek the source of the water intrusion. corrosion in a tendon with a grout void. example of corrosion caused by water After reaching around 40 psi, water traveling along the strand and duct into began discharging out of the top deck the voided area. In areas where road of the bridge (soap was placed around deicers are used, this phenomenon area to make any exiting air visible). This is a major concern. Once project evidence demonstrated that the water- stakeholders became more aware of this filled ducts were being recharged through issue, inspections were performed more cracks in the bridge deck. regularly on this structure’s PT tendons. Analysis of the damaged condition by One of the most prevalent design qualified engineers is also prudent. problems in PT bridges is scuppers and deck drainage systems that run inside Noteworthy Findings the structure or terminate at critical Inspections of structures constructed locations on the superstructure. Over during an era with lower grouting time, these drains fail, transferring installation standards and supervision road deck debris and water either Figure 3. Operation to find cracks in the bridge illustrate how tendons that were poorly to the interior of the structure or that were leading to moisture in post-tensioned grouted have held up over time. These tendons. structures were of different construction types, ranging from precast segmental concrete to cast-in-place concrete boxes on falsework and straddle bents. In one Midwestern state, 17 structures and 233 tendons were inspected. The tendons contained 466 anchorages and 340 high points. For all of the bridges and tendons inspected in this state, 61 voids were located—with some being in the same tendon at different locations. Despite the number of voids found, there were no documented strand or tendon failures in these structures, most likely because of details of the structural high quality of the structure’s upkeep. The owner is currently in the process of having the voided areas grouted and the decks sealed to lengthen the service life of these structures.

Inspections by the author have also revealed that a substantial number of Figure 4. Equipment used to pressurize tendons the observed tendons with section loss Figure 5. Signs of tendon corrosion near a bridge and find the source of water. arose from conditions outside of the drainage system.

ASPIRE Spring 2019 | 29 at eliminating problems with improper materials and incorrect installation of grouted systems. These efforts have served to better educate all parts of the industry and to improve grouting quality. PT tendons are now being grouted under strict guidelines, and detailed reports are required on the grouting operation itself. Testing throughout the operation is required in most states; therefore, if any issue arises in the future, it should be possible to retrieve the original records for investigations. The current state of the practice for grouting can be found in PTI M55.1-12, Specification for Grouting of Post-Tensioned Structures, as well as PTI/ASBI M50.3-12, Guide Specification for Grouted Post-Tensioning. These documents, in addition to ASBI and PTI installer certification programs, are major resources for owners that are building and Figure 6. Condition of post-tensioning tendons inspected by the author by construction time period. maintaining PT structures. onto the superstructure (Fig. 5) . the concrete to deteriorate, followed Figure 6 presents the conditions Cracks consistently exposed to outside by corrosion of the duct and ultimately of the PT tendons investigated by the contaminants such as road salts and corrosion of the tendon. There was no author grouped by the date of original chlorides will grow, further endangering indication of voids being originally present construction. The vertical axis has been the tendon. in the failed area. shortened to focus on the upper limits to allow the small quantities to be visible. One example of a bridge with a PT Advancements in Even though data in the figure are just system with severe tendon corrosion Post-Tensioning for structures inspected by the author, was the Cline Avenue Bridge, a cast-in- Although tensioning of the tendons is it is evident that the condition of the place concrete box structure built on perhaps the most important factor for structures significantly improved over falsework. For several years before the the strength of the structure, grouting time with refinement of PT systems and tendon failure was found, inspections had is the most critical for the lifespan and procedures, as indicated by the reduced noted deterioration, which was related durability of the structure. In the current incidence of voids in tendons. to a leaking drainage system. Staining era, several modifications have been was visible on the wall where the water made to improve PT installation and Conclusion collected because the structure did not help eliminate issues in the tendons. One After decades of inspecting PT systems, contain drain holes. Also, layers of salt major achievement was the introduction the author can comfortably assert were visible on the floor from the leakage of the plastic extruded duct material with that, when properly designed, detailed, and rehydration process. At some point, airtight sealed connections. This innovation and installed under the guidelines and workers tied rags wrapped with duct tape helps prevent intrusion of water or any procedures published as consensus-based to the leaking drainage pipe in an attempt outside contaminants into the tendons. best practices by industry leaders, PT to seal it. When it was determined that Another advancement was the introduction structures are durable, reliable, and tendons were located in the same area as of prepackaged thixotropic grouts. These cost-effective options for many bridge the leak, an inspection was performed. new grouts have limited chloride content, projects. Within the last 20 years, low permeability, zero bleed and excellent significant innovations and improvements When the Oneida River Crossing structure pumpability in normal grouting operations. in PT systems have resolved challenges was inspected in 2007, a few tendon encountered when the technology was failures were identified. This structure Another achievement over the past 30 new and spurred growth in the industry. is one of the oldest PT girder-type years has been the proactive approach of As a result, today’s PT systems are structures in the United States, built in the American Segmental Bridge Institute designed and constructed to withstand the 1960s. In this case, the drain scuppers (ASBI) and the Post-Tensioning Institute severe conditions. were terminated just above the girder (PTI) to improve the quality of grouted ______flange and the tendons were encased PT structures. These two institutions in a galvanized metal duct. Years of have developed and continue to refine Bruce Osborn is a field superintendent deicing salts applied to the roadway and grouting specifications and procedures as for Structural Technologies LLC/VSL in spreading onto the concrete flange caused well as field certification programs aimed Manassas, Va.

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ASPIRE Spring 2019 | 31 CONCRETE BRIDGE TECHNOLOGY Seismic Behavior of Reinforced- Concrete-Filled Steel Tubes by Dr. Mervyn J. Kowalsky, North Carolina State University

Research on concrete-filled steel tubes is vast and has been conducted for 0.04 many decades. Over the last 10 years, a 0.035 research program undertaken at North Prior to Carolina State University (NC State) 0.03 Fracture has aimed to investigate the seismic performance of reinforced-concrete- 0.025 filled steel tubes (RCFSTs). The system involves a reinforcing bar cage that is 0.02 placed inside a steel shell, which is then filled with concrete. In the research done 0.015 at NC State, both spirally welded and straight-seam pipe have been studied, 0.01 Prior to

with diameter-to-wall thickness ratios Longitudinal StrainsTensile Buckling (D/t) varying from 32 to 192. As noted 0.005 in the companion article in this issue of 0 ASPIRE® on the Brotherhood Bridge near Juneau, Alaska, the use of RCFSTs 0 50 100 150 200 D/t Ratio is common in Alaska, as well as other states. In the case of Alaska, the RCFST Strain limit states as a function of tube diameter/wall thickness ratio (D/t). Figure: Nicole Brown. system is preferred for bridge design for several reasons: states such as buckling and rupture of interaction facility at NC State.5,6 • The steel tubes serve as the formwork the tube wall. This setup allowed the soil stiffness to for the piles/columns. be modified by prestressing the sand • The steel tubes can be used in driven Initial tests at NC State on RCFSTs between two concrete plates. Each or drilled foundation applications. were conducted where the test units were specimen was subjected to reversed • The steel tubes provide high levels subjected to reversed cyclic four-point cyclic lateral loads during testing. of confinement, thus resulting in bending.1–4 The span between actuators Damage levels were similar to what large deformation capacity, which was adjustable to account for different was observed for the initial four-point is important for good seismic constant-moment regions, which in turn bending tests. performance. model different soil stiffnesses. In total, • The system has less environmental 30 RCFST specimens were tested: 22 In addition to tests on the below- impact than conventional substructures were 2 ft in diameter and 33 ft long, and ground hinge, the RCFST column-to- requiring larger cofferdams. eight were 10¾ in. in diameter and 14 ft cap connection, which was developed • Construction is simplified because the long. Four of the tests were conducted at at the University of California, San steel tubes serve as piles below the –40°C (–40°F) to investigate the RCFST Diego, in the 1990s, was subjected to soil surface and as columns above the behavior at wintertime temperatures simulated seismic forces at NC State at ground level. typical of Alaska. temperatures as low as –40°C (–40°F). The connection, which leaves a gap When subjected to lateral demands, these The testing program showed that tube wall between the RCFST shell and the bottom RCFST systems may develop plastic buckling is strongly dependent on the D/t, of the cap, was shown to perform well hinges at the connection to the cap beam while fracture occurs at an approximately at low temperatures. Recommendations as well as below grade at the point of constant strain, irrespective of D/t. In on material strength and plastic hinge maximum moment. Therefore, research all cases, tube wall local buckling was lengths as a function of temperatures has been directed toward developing followed by tube fracture. The energy typically encountered in Alaska were also guidelines for the designs of these dissipation capacity of these systems was proposed.7 Combined with the extensive regions. Among the parameters that have also shown to be large. research on the RCFST itself, the been investigated are below-grade plastic system has been deployed in numerous hinge length, energy dissipation capacity, The next series of tests focused on Alaska bridges over the last 20 years. and quantitative measures of key limit RCFSTs in soil using the soil-structure Approximately 20 multispan bridges with

32 | ASPIRE Spring 2019 guidelines have been developed for RCFST seismic design. Recommendations have included strain limits, plastic hinge lengths, and analysis methods. References 1. Gonzalez, L., M.J. Kowalsky, J.M. Nau, and T. Hassan. 2008. Reversed Cyclic Testing of Full Scale Pipe Piles. Report to Skyline Steel Corporation. Report IS 08-13. 52 pages. 2. Gonzalez, L., M.J. Kowalsky, J.M. Nau, and T. Hassan. 2009. Reversed Cyclic Testing of Small Scale Pipe Piles. Report to Skyline Steel Corporation. Report IS 09-12. 53 pages. 3. Brown, N.R, M.J. Kowalsky, and J.M. Nau. 2013. Strain Limits for Concrete Filled Steel Tubes in AASHTO Provisions. Final report to Alaska University Transportation Center/ Alaska Department of Transportation and Public Facilities. http://dot. alaska.gov/stwddes/research/assets/ pdf/fhwa_ak_rd_13_05.pdf. 4. Brown, N.R, M.J. Kowalsky, and J. Nau. 2015. “Impact of D/t on Seismic Behavior of Reinforced Concrete Filled Steel Tubes.” Journal of Constructional Steel Research. 107: 111–123. DOI: 10.1016/j Test setup to model reinforced-concrete-filled steel tubes in soil. Figure: Diego Aguirre. .jcsr.2015.01.013. RCFST piers were located within areas experienced any damage or signs of 5. Aguirre-Realpe, D.A., M.J. Kowalsky, having a peak ground acceleration greater significant movement. J.M. Nau, and M. Gabr. 2017. than 0.25g during the 7.0-magnitude Seismic Performance of Reinforced earthquake event on November 30, In summary, based on research over a Concrete Filled Steel Tubes in Soil. 2018. Even though many of these bridges 10-year period that indicated good Final report to Alaska Department of were located in liquefiable soils, none performance of these systems, design Transportation and Public Facilities. http://dot.alaska.gov/stwddes/ Deformation of reinforced-concrete-filled steel tube during test in soil. Photo: Diego Aguirre. research/assets/pdf/4000-127.pdf. 6. Aguirre-Realpe, D.A, M.J. Kowalsky, J.M. Nau, M. Gabr, and G.W. Lucier. 2017. “Seismic Performance of Reinforced Concrete Filled Steel Tube Drilled Shafts with Inground Plastic Hinges.” Engineering Structures. 165: 106–119. DOI: 10.1016/j .engstruct.2018.03.034. 7. Montejo, L.A., L.R. Gonzalez-Roman, and M.J. Kowalsky. 2012. “Seismic Performance Evaluation of Reinforced Concrete-Filled Steel Tube Pile/Column Bridge Bents.” Journal of Earthquake Engineering. 16(3): 401–424. DOI: 10.1080/13632469.2011.614678. ______

Dr. Mervyn J. Kowalsky is a professor of structural engineering at North Carolina State University in Raleigh.

ASPIRE Spring 2019 | 33 CONCRETE BRIDGE TECHNOLOGY Sarah Mildred Long Bridge Tower Foundation Construction by Joseph Orlando, Cianbro Corporation

The new Sarah Mildred Long Bridge, of Cianbro, see the Spring 2017 issue Others have approached the construction which spans the Piscataqua River from of ASPIRE®). FIGG Bridge Engineers of these types of foundations using the Portsmouth, N.H., to Kittery, Me., opened designed the approach spans, and following methods: on March 30, 2018. The structure has Hardesty & Hanover designed the lift • Casting a complete tub and setting it two-level precast concrete segmental box- span and towers as a joint venture. on drilled shafts using a large capacity girder approach spans with a 300-ft-long crane lift span. Additionally, the 200-ft-tall towers Tower Foundation Design • Casting and launching a complete tub, of the lift span are vertically post-tensioned Challenges floating it over the drilled shafts, and segmental towers, a first in the United The Piscataqua River is a deep and fast- then submerging it into place States. The foundations for the lift span flowing tidal river, one of the fastest • Suspending a precast concrete towers are 125 ft long, 65 ft wide, and in the United States. This factor and segmental soffit above high water, 15 ft thick. The design of the foundation others presented many challenges to the building a traditional cofferdam on the includes a precast concrete tub used as a construction of the tower foundations. soffit, and using synchronous jacks to cofferdam and form. An allowance of 18 The following were among the primary lower the system into place in. for the tub-wall thickness and 3 ft for considerations that influenced the the bottom thickness was included in the ultimate method of foundation Cianbro analyzed these options and design. Eight 10-ft-diameter drilled shafts construction: ruled them out because it did not have socketed 35 ft into competent rock support • The tidal current could exceed 4 knots. sufficient crane capacity to lift 1100 tons, each foundation. The top of the foundation • The maximum crane capacity at and a dry dock or launching system was is at elevation 8 ft, about 2 ft above the working radius using a Manitowoc not available to fabricate and launch highest astronomical tide expected during MLC300 Lattice Boom Crawler, which such a large floating tub. Additionally, construction. Each of the structural was the largest crane the contractor the Piscataqua River’s extreme current footings contains 3200 yd3 of cast-in-place had in its fleet, on a 72 ft by 200 ft and a slack tide of only 30 minutes made concrete and 500,000 lb of reinforcement deck barge was 180 tons. the prospect of floating and accurately along with 14 post-tensioning ducts for the • The foundation had to be submerged positioning a large tub over the drilled segmental towers. 13 ft at the highest astronomical tide. shafts too risky. Similarly, slowly jacking • The water was 65 ft deep, with little a tub down into the current was not ideal. The project was jointly sponsored by the overburden on the river bottom. Maine and New Hampshire departments • There were significant construction Cianbro Solution of transportation. The project delivery and environmental loads, such as A precast, sand-lightweight concrete, method was the construction manager/ water pressure due to the tidal current segmental post-tensioned tub addressed general contractor method, and the alternating in direction. the design challenges. The MLC300 Cianbro Corporation of Pittsfield, Me., • Worker and diver safety had to be crane could quickly erect the tub. The was the general contractor (for a profile ensured. combination of strength and density of the sand-lightweight concrete was critical Sarah Mildred Long Bridge approaches, lift span, towers, to the success of the design because loads and tower footings. Photo: Cianbro/Richard Hopley. were close to crane capacity. Additionally, each piece could be set quickly to the design elevation and secured during slack tide. The tubs were free draining, which gave workers two hours to work inside the tubs at low water. Workers grouted and bolted the tubs from the top. There was no need for divers to go beneath the tubs, thereby improving safety.

Each precast concrete segmental tub, one for each tower, was composed of nine segments: five drilled-shaft units and four fill units. The drilled-shaft units used strongbacks with hangers to support the segments from the top of the drilled shafts. For erection, the fill

34 | ASPIRE Spring 2019 Installation of the drilled-shaft units. Photo: Fill unit installation. Photo: Cianbro. Nose unit installation over a drilled shaft. Cianbro. Photo: Cianbro. units were placed between the drilled- piece) to be transferred to the drilled-shaft shaft units and were supported by an unit through shear friction. An extensive integral ledge cast into the drilled-shaft finite element model was developed of the units. The drilled-shaft segments could tub using RISA-3D software to determine be precisely located in elevation and the structural behavior of the tub. plan by using threaded hangers and horizontal alignment fixtures cast into the The success of the system depended on concrete around the penetrations for the the connection of the tub to the drilled drilled shafts. The horizontal alignment shafts. The connection was required fixtures also stabilized the segments from to transfer large uplift forces from the pressure of the water current. A ¾ the dewatered tub as well as the loads in. space between segments provided imposed from concrete placement. The The dewatered tub with the drilled shafts visible. erection tolerance and space to grout and design shear load transferred to each The work platform has been attached to the top seal between segments. Grade 75, 1-in.- drilled shaft was 850 kip. A grouted shear of the tub. Photo: Cianbro. diameter sleeved all-thread bolts were key design, typically used in the offshore spaced at 18 in. along the entire length oil industry, provided the necessary before a segment was set allowed the of the joint between segments. Each all- capacity. The connection was designed divers to grout the connection from the thread bolt was post-tensioned to 30 kip using grouted pile-to-structure connection top. High-strength (8 ksi), structural after the joints were grouted, allowing the criteria from the American Petroleum underwater concrete, with washout entire load of the fill unit (weight of first Institute's Recommended Practice additives, provided the required strength lift of concrete plus dead load of the fill 2A-WSD.1 Installing forms for grouting in a timely manner in the cold river water. Conclusion The precast concrete, post-tensioned segmental tub provided a cofferdam/ form system that was constructed using readily available erection equipment. Tub erection, grouting, and dewatering took only 30 days, which helped meet an aggressive project schedule. Exposure to the harsh environmental conditions was minimized, thereby reducing risk. The use of sand-lightweight concrete was also critical to the success of the design. Reference 1. American Petroleum Institute (API). The precast concrete segmental tub. The use of sand-lightweight concrete for the segments allowed the 2014. API Recommended Practice tub to be installed using readily available equipment. Figure: Cianbro. 2A-WSD: Planning, Designing, and Constructing Fixed Offshore Platforms—Working Stress Design. DRILLED SHAFT DRILLED SHAFT UNIT 22nd ed. Washington, DC: API. 3 1 3 4" 14'–102" 4" ______EL -4.50 Joseph Orlando is senior structural engineer with Cianbro Corporation in Portland, Me. 4' EDITOR’S NOTE

FILL UNIT

1" ALL THREAD@18" More information on the Sarah Mildred Long Bridge is contained Typical segment joint detail. The fill unit of the tub was placed on an integral ledge of the drilled-shaft in a Project article in this issue of unit during erection. Later, the joint was grouted and post-tensioned. Figure: Cianbro. ASPIRE on page 24.

ASPIRE Spring 2019 | 35 CONCRETE BRIDGE TECHNOLOGY Implementation of an Electrically Isolated Tendon Post-Tensioning System in the United States

by Dr. Clay Naito, Lehigh University, and Dr. Christina Cercone, Manhattan College

Post-tensioned concrete bridges represent The tendon system uses a plastic duct, resistance (LCR) meters to measure an important component of the current with plastic duct couplers and plastic the AC resistance, capacitance, and loss U.S. bridge inventory. These systems, half shells to protect the integrity of the factor between the isolated PT strands whether cast-in-place or precast concrete corrosion protection system along the and the reinforcing steel located in the construction, can be used to create long- length of the tendon. The plastic half surrounding bridge structure. These span continuous bridge superstructures shells are used between the plastic duct readings can be compared to limiting with long service lives. However, ensuring and the transverse reinforcement to acceptance criteria values1 to provide the quality of the post-tensioning duct provide additional protection to the duct owners with an assessment of the quality system and grout material used to during member fabrication and tensioning. of the encapsulation and any unexpected encapsulate the strands has been a corrosion initiation. These measurements concern. The post-tensioning ducts are Several companies commercially produce are often taken at key stages of conventionally located within the web of the required components of the EIT construction, such as during tensioning or the concrete girders, and critical sections— system for the European market, making tendon installation, before and after grout such as splices and anchorages—are this an off-the-shelf technology. For the installation, during deck placement, and heavily reinforced to provide adequate past 20 years, EIT systems have been during service. The EIT system has the transfer of forces into the members. These used in various post-tensioned concrete potential to provide long-term condition practical requirements of post-tensioning bridges in Europe, including the Piacenza assessment of the tendon system over the (PT) make visual and nondestructive Viaduct and Marchiazza Viaduct in life of the bridge. inspection techniques difficult to implement Italy and the P.S. du Milieu and the during construction and throughout the Wiesebrücke Basel in Switzerland. First U.S. Demonstration life of the bridge. Quality control methods Project are well established for PT installation With the EIT system, the encapsulation The many benefits of the EIT system and grouting, but traditional inspection system is assessed from time of and its successful use in Europe have methods are not easy to implement during construction through the service life prompted research and development regular service-life inspections of internal of the bridge by using commercially efforts geared toward implementation in tendons. available inductance/capacitance/ the United States, including a series of

To address this issue, electrically isolated tendon (EIT) systems have been developed. These systems, which can be easily integrated into new construction, provide full electrical isolation of the steel PT tendons from the surrounding concrete of the bridge structure. With isolation, the PT steel cannot form a corrosion cell with the exterior reinforcement, and corrosion of the tendon is nearly eliminated because the amount of oxygen within the duct is low. System Components The EIT system is composed of an enhanced tendon and anchorage system. The anchorage includes an isolation The main unit of the Coplay-Northampton Bridge consists of a 540-ft-long, three-span section over plate, a plastic trumpet, and proper the Lehigh River. The superstructure consists of five prestressed concrete PA bulb tees, which were encapsulation of the anchorage head. spliced and post-tensioned. All Photos: Dr. Clay Naito.

36 | ASPIRE Spring 2019 Post-tensioning anchorages in precast concrete beams during Post-tensioning splice prior to placement of the closure joint. No difference can be seen spiral reinforcement installation, with an electrically isolated between the electrically isolated tendon at the top and the three conventional tendons below. tendon trumpet (top) and a traditional trumpet (bottom). demonstration bridge projects sponsored each beam. Electrical continuity along a viable approach for providing additional by the Federal Highway Administration the entire span is important because the quality assurance of the PT system. (FHWA). The first demonstration measurements are taken at one end of project integrates the EIT system into the bridge. Failure to maintain electrical References the Lehigh County–owned Coplay- continuity of some spans would limit 1. Angst, U., and M. Büchler. 2015. Northampton Bridge between Coplay and the effectiveness of the EIT system. Monitorable Post-Tensioning Systems Northampton boroughs in Pennsylvania. The continuity strands were tied to the Sub Task 2: State of the Art Report. This construction project is currently uncoated steel shear reinforcement within Zurich, Switzerland: Swiss Society for underway. Deck placement is expected in each beam during precasting and were Corrosion Protection. spring 2019, and the bridge is scheduled tied together at each splice after erection. 2. Post-Tensioning Institute (PTI) and to open in fall 2019. The two electrical continuity strands were American Segmental Bridge Institute located at the bottom of the beams. (ASBI). 2012. PTI/ASBI M50.3- The primary portion of the Coplay- 12: Guide Specification for Grouted Northampton Bridge consists of a three- The EIT system was monitored during Post-Tensioning. Farmington Hills, MI: span, 540-ft-long unit over the Lehigh selected stages of the construction PTI. River. The superstructure consists of project (following tensioning of the ______prestressed concrete PA bulb tees, tendons, prior to and following grouting, Dr. Clay Naito is a professor in the which were spliced and post-tensioned and 28 days after grouting), and Department of Civil and Environmental in the field. The beams were precast at monitoring will continue to evaluate the Engineering at Lehigh University in Northeast Prestressed Products in long-term performance of the PT system. Bethlehem, Pa., and Dr. Christina Cercone Cressona, Pa. The bridge was designed Measurements are taken by connecting is a faculty member in the Civil and by AECOM and constructed by Trumbull the LCR meter to one of the exposed Environmental Engineering Department at Corporation, with project management continuity strands located at the bottom Manhattan College in Riverdale, N.Y. provided by Pennoni. Each beam has of the flange and to the PT strands of four PT ducts. As a demonstration, the EIT system, using an exposed wire only the top PT duct in each beam line connection. These measurements are has the EIT system, which was provided compared to the threshold performance by DYWIDAG-Systems International limits and indicate the level of electrical (see the Focus article in this issue of isolation of the tendons. ASPIRE® on page 6). Initial measurements indicate that the As mentioned previously, the EIT system EIT system meets the current isolation requires the use of a plastic duct with requirements needed to achieve the highest plastic duct couplers and plastic half level of corrosion protection, PL3, as shells. In the demonstration project, defined in PTI/ASBI M50.3-12: Guide the addition of the required isolation Specification for Grouted Post-Tensioning2 plate and plastic trumpet in the EIT and additional recommendations developed anchorage was not a significant change by Angst and Büchler for FHWA.1 to a traditional PT system. All the PT ducts, including the single EIT duct, were According to discussions with the spliced in the field using plastic couplers precast concrete producer, project Measurement of the electrically isolated tendon combined with heat-shrink tubing. To manager, contractor, and Pennsylvania (EIT) system after grouting. The inductance/ ensure electrical continuity of the beam Department of Transportation, the use of capacitance/resistance meter is connected to the reinforcement located outside of the PT the EIT system required minimal added exposed steel located at the bottom flange and ducts, two uncoated pretensioning strands construction effort, has had nominal to the post-tensioning strands using the wire were left protruding from each end of impact on project costs, and appears to be connection to the top EIT anchorage.

ASPIRE Spring 2019 | 37 CONCRETE BRIDGE TECHNOLOGY Sweep in Precast, Prestressed Concrete Bridge Girders

by Dr. Bruce W. Russell, Oklahoma State University

Sweep is defined in the Manual for Quality and owners may be understandably would be preferable). The measurement(s) Control for Plants and Production of concerned about how sweep could occur should be recorded even if zero. Structural Precast Concrete Products in production, and what corrective actions (PCI MNL-116)1 as “a variation in can, or should be taken. Regardless the Alternatively, it may be easier to measure horizontal alignment from a straight amount of sweep, the truth is this: most the sweep at approximately 20 ft line parallel to centerline of member prestressed concrete bridge girders, once increments. In this case, measurements 1 (horizontal bowing).” A generalized they are in place with composite concrete should be made accurate to ± ⁄16 in. A representation for sweep is shown in Fig. 1. decks cast upon them, will function sweep measurement made at the center of effectively for the design life of the bridge a 20.0-ft length, or the average of several Decades of industry experience inform us without concern for limits on strength, such measurements, can be converted to that very few girders are produced with durability, or serviceability. an overall sweep by the following: noticeable or out-of-tolerance sweep. 2 However, when sweep is large enough to Prestressed concrete bridge girders that ⎛ L ⎞ be noticed—or when the amount of sweep are built in accordance with our design f = f ⎜ ⎟ 20 20.0 ft exceeds tolerance—producers, contractors, standards, and are made from conforming ⎝ ⎠ materials (concrete and steel) within a where geometry described by the contract f = sweep projected over the documents, will support the intended entire girder length L

design loads for millions of cycles, in all f20 = sweep measured over a kinds of climates, for the design service 20.0 ft length life of the structure. This article focuses on the sweep of bridge girders that may Tolerances for precast, prestressed concrete occur during initial fabrication, lifting, or members have been established to allow storage in the yard. One probable cause for production and erection variances, as is explored with a hypothetical example well as the interface of the member with and corrective actions that can be taken the overall construction of the structure. L Sweep while the girder is still in the precast Tolerances are to be used for guidelines producer’s yard. Subsequent articles and not as reasons for rejection. If the will cover transportation, erection, and girder can be brought within tolerance in construction issues and discuss whether an acceptable manner, or if exceeding the permanent sweep in girders should cause tolerance does not affect the integrity or concern for long-term stresses, strength, performance of the girder, the girder should or performance. be accepted. Later articles will show that girders with sweep in excess of tolerances Measurements and Tolerances can function without compromising the The initial measurement of sweep is completed bridge system. made after the side forms are removed and prestressing force is transferred, or The tolerance for sweep for bridge girders 1 1 after the girder is removed from the forms given in MNL 116-99 is ⁄8 in. per 10 and is placed on dunnage in the precast ft. For example, a bridge girder with a producer’s yard. When measuring sweep, it length of 130.5 ft would have a sweep is important that the girder is level, the sun tolerance of 1.63 in. The calculation for is not shining on one side, and the actual sweep tolerance follows: flange widths have been verified at the ends ⎛ 1 ⎞ and middle. Commonly, sweep is measured ⎜ in.⎟ 8 CL at the midspan of the girder. Admittedly, Sweep Tolerance = 130.5 ft⎜ ⎟ ⎜10 ft ⎟ accurate measurement may be difficult for ⎜ ⎟ Figure 1. A generalized representation for sweep ⎝ ⎠ long girders. However, a measurement to in a girder. Figure: Dr. Bruce Russell. 1 = 1.63 in. ¼ in. precision should be sufficient ( ⁄8 in.

38 | ASPIRE Spring 2019 What Causes Sweep and What action. An investigation by the producer calculations compute the amount of Should Be Done? should include checking or reviewing the sweep f that results from the minor-axis Sweep can be caused by a number of following: bending moment induced by the ¼ in. factors, including eccentric prestressing • Form alignment. eccentricity of strands assuming thirty- force, the misalignment of forms, • Cross-section dimensions in several eight 0.6-in.-diameter strands with an anomalies in locations or positions of locations along the length of the forms. effective prestressing force of 1512 kip lifting devices, differences in material • Strand locations—ensure templates after elastic shortening loss: properties within the girder, variation in are centered and that holes have not concrete maturity at early ages, exposure elongated. F e = 1512 kip 0.25 in. to sunlight, out-of-level supports, or • Uniform pretensioning of strands and pe x ( )( ) − differing curing conditions. uniform application of prestressing = 378 kip in. forces. F e 378 kip −in. Based on previous experience, each • Plumbness of girder and level bearing φ = pe x = y E I 4821 ksi 37,543 in.4 producer should be aware of what amount surfaces in storage—a girder that is ci yy ( )( ) − of sweep is normal for a particular girder stored out of plumb can develop sweep. = 2.088 ×10 6 rad/in. type. When the initial measured sweep • Exposure to sun—thermal differences φ L2 is larger than this “experience” value, between the sides of the girder in f = y or if measured sweep exceeds tolerance storage can cause sweep. 8 2 or is projected to exceed tolerance, then • Curing temperatures—if heat is 2 ⎛ in. ⎞ 2.088 ×10−6 rad/in. 130.5 ft ⎜144 ⎟ an investigation should be undertaken applied, ensure uniform application of ( ) 2 ( ) ⎝ ft ⎠ immediately by the precaster and sweep elevated temperatures. = 8 should be monitored on a regular basis • Quality control records—search for while the girder is stored. The investigation differences in concrete batches. = 0.640 in. might uncover a problem that can be • The design—strand pattern and From these calculations, one can see that a corrected before subsequent girders are items such as blockouts in a flange or strand pattern that is placed eccentrically produced or, if mitigating or corrective localized changes in the web. by ¼ in. can produce an estimated sweep action on the existing girder is required, of 0.64 in. immediately after transfer. This lead to a preferred course of action. As In many cases, the cause of sweep is sweep is less than the sweep tolerance of time goes by, measured sweep may worsen not easily identified. It could involve a 1.63 in. for a 130.5 ft girder, which was because of creep and concrete maturity, combination of two or more of the listed calculated earlier in this article. with fewer opportunities for corrective items. The sweep created by the eccentric Table 1. Girder Design Details for Example Calculating Sweep for prestressing force creates a theoretically

Bridge: SH 99 over Deep Fork River, Eccentrically Located Strands uniform minor-axis curvature φy over Lincoln Co., Okla. For the purposes of this discussion, one the length of the bridge girder. As can Design Engineer: Bruce W. Russell possible cause of sweep is explored. The be seen in the calculations, sweep is example is based on a PCI-AASHTO proportional to the square of the girder Span: 130.5 ft bulb-tee BT-72 girder2 designed for State length. Therefore, in the author’s opinion, Type of Girder: PCI-AASHTO BT-72 Highway 99 (SH 99) over the Deep for longer girders, it may be more Spacing, s = 7.17 ft Fork River in Lincoln County, Okla. The appropriate to set a larger tolerance for original designs were performed by the sweep than the 1⁄ in. in 10 ft provided A = 767 in.2 8 author. Spans for this bridge were 130 in MNL 116-99. For example, the h = 72.0 in. ft 6 in., measured from center-to-center same strand eccentricity that creates a

cb = 36.60 in. of bearings. Girders were spaced at 7 ft ¾ in. sweep for a 100 ft girder (which I = 545,113 in.4 2 in. Each BT-72 girder was made with exceeds the tolerance of 1.25 in.) also xx thirty-eight 0.6-in.-diameter Grade 270 produces a 3.0 in. sweep for a 200 ft I = 37,543 in.4 yy prestressing strands conforming to ASTM girder, which exceeds the tolerance of

wb = 0.799 kip/ft A416. Design details are listed in Table 2.50 in. The point is that longer girders 1. Please note that the example used for are more susceptible to noticeable or f’c = 10.0 ksi f’ = 7.0 ksi this article is hypothetical and created out-of-tolerance sweep simply because ci only for purposes of illustration. During they are longer, and the effect that may E = 4821 ksi ci fabrication of the actual girders for the have caused sweep in the first place is Width of 26 in. SH 99 Bridge, there were no reports of squared in proportion to length. bottom flange sweep in the bridge girders. Width of Stresses Caused by Sweep 42 in. top flange For purposes of illustration, let us Generally, if sweep exists, it is most often Strand type: 0.6-in.-diameter Gr. 270 compute the sweep as if all strands in small, and its effects on stresses can ASTM A416, low relaxation the girder were located ¼ in. off center, be ignored. Also when considering the or with a lateral eccentricity e of ¼ magnitude of the stresses, readers should N = 38 strands x in., which is the tolerance in PCI MNL- be aware that the stresses computed in e = 29.02 in. 116 for strand placement. The following this manner are temporary stresses and,

ASPIRE Spring 2019 | 39 accordingly, the importance of temporary Creep Considerations we should conclude that it is possible that stresses should not be overemphasized Because of concrete’s relative immaturity tolerance for sweep may be reached and in judging the performance of precast, at early ages, we know that the concrete exceeded, although, as mentioned earlier, prestressed concrete bridge girders. will experience the largest creep strains at the project from which the example girder early ages. Creep also can have significant is taken had no reported issues with sweep, The earlier computations of the sweep effects on prestressed concrete because the which is typical of the great majority of caused by an eccentric prestressing force prestressing forces remain active over the bridge projects. resulted in a lateral curvature of 2.088 × life of the bridge. Similarly, the girder sweep 10–6 rad/in. If this curvature is extended measured initially is affected by the creep Recommendations to to the outer edges of the bottom fiber, properties of concrete, and so discussion of Mitigate Sweep strains at the extreme fibers would be: creep within this article is important. Sweep in a girder is not typically a large concern, but it can affect handling,

− rad In the example provided, the estimated transportation, erection, and stability ε =± 2.088 ×10 6 ×13 in in. sweep of 0.64 in. that would be caused issues even when the measured sweep is by a ¼ in. eccentricity of prestressing within tolerance.4 For many reasons, the − in. =± 27 ×10 6 force is less than the 1.63 in. tolerance. engineer, owner, or precaster may want in. Those involved must draw from their own to reduce the sweep of the girder to ease experience to judge whether sweep is any handling, lifting, transportation, or This strain would produce 131 psi of “normal,” but this author will argue that erection issues. When a decrease in the additional compressive stress on one side the estimated sweep is not “excessive.” amount of sweep in a girder is desired, of the bottom flange and reduces the Nonetheless, even “normal” amounts the early age of the concrete and its compressive stress on the opposite side by of sweep may merit consideration for self-weight enable corrective actions. The 131 psi. At the top flange, an additional a proactive approach when considering recommendations for corrective action tensile stress of 211 psi will theoretically the effects of creep. Immediately after fall into two categories: be produced on one side. transfer, and upon initial storage at the 1. Straighten the girder with bracing and precast producer’s yard, the concrete forces, or Now, some engineers may be tempted to is young and the internal crystalline 2. Store the girder on slightly sloped include additional sources of tension structures that provide concrete strength supports and allow its self-weight to in their calculations. However, one must are maturing rapidly. As the concrete straighten the girder. bear in mind that these calculations are creeps with time, the sweep is also approximations and represent mere expected to increase. To straighten the girder using direct estimates for the stresses and strains that application of force, the girder must be may actually occur within bridge girders. Table 2a provides a summary of braced at the ends to provide a reaction to Accordingly, I argue that additional assumptions and Table 2b are the the straightening force applied at midspan calculations for stress and strain based calculations performed to estimate the or intermediate points. A structural frame on possible sweep deformations are increase in sweep caused by creep at will likely be required to provide both relatively unimportant and should not be various ages. Data in the table show the straightening forces and reactions, or the used to make additional requirements for additional sweep that can occur within the girder with sweep can be braced against computation, for load conditions, or for first 28 and 90 days for the BT-72 girder other girders. It is also important that the handling. Instead, this calculation serves as being used as an example in this article. straightening force be applied through the a reminder to place reinforcement where Considering only the “within tolerance” centroid of the cross section; if it is not, tension exists in order to control cracking sweep of 0.64 in. caused by offset the application of force will cause torsional and provide better distribution of stresses prestressing strands, and using provisions in deformations. In the example provided for and strains throughout the cross section. the current AASHTO LRFD specifications3 the 130.5-ft-long BT-72 girder, the lateral It is my firm opinion that if the engineer for creep calculations, we can see that the midspan force required to straighten has provided sufficient reinforcement in sweep deformation nearly doubles in 90 the girder would be about 1450 lb. The the tensile zone of a precast, prestressed days, to 1.24 in. At this level of sweep, the sweep must continue to be monitored, and concrete bridge girder, and if that design bridge girder is approaching the tolerance it is likely that the force will have to be is in accordance with current American limit of 1⁄ in. per 10 ft. of length (that maintained over the full time of storage to Association of State Highway and 8 is, 1.63 in., as computed previously). straighten the girder prior to transportation. Transportation Officials’ AASHTO LRFD Additionally, various other potential effects Bridge Design Specifications3 for temporary may combine to increase sweep, and many Alternatively, the girder can be straightened stresses, the additional tensile stresses of these effects may be unknown. Therefore, by storing the bridge girder on a slight created by sweep in girders can be ignored. Table 2a. Summary of assumptions. Table 2b. Effects of Creep at 28 and 90 Days Using AASHTO LRFD Article 5.4.2.3.2.

1 RH = 70 % Age (days) Creep coefficients Sweep f from ± ∕4 in. eccentric Time Development Creep Coefficient prestressing force and creep (in.) V/S = 3.01 in. Ψ Factor ktd (t, ti) k = 0.625 f 1 – – 0.64

ks = 1.06 ≥ 1.0 28 0.467 0.587 1.02

khc = 1.00 90 0.738 0.929 1.23

40 | ASPIRE Spring 2019 angle. In this method, the girder’s self- beam during storage can then be susceptible to time-dependent changes, and weight will work over time to straighten the computed as the ratio of wy to the provides an outline for corrective action, if beam. At the very least, storing the girder weight of the girder wb: that is desired. with a slight tilt will prevent creep effects w from worsening the initial sweep. y 0.0178 kip/ft θ = = = 0.0223 rad References wb 0.799 kip/ft 1. Precast/Prestressed Concrete The method for straightening a girder by Institute (PCI). 1999. Manual Using this procedure, the supports for storing on canted dunnage is described for Quality Control for Plants and this bridge girder in storage should as follows. (Calculations shown are for Production of Structural Precast be sloped at ϴ, or approximately ¼ in. the BT-72 beam with an initial sweep of Concrete Products, 4th ed. (PCI per 12 in., or approximately ½ in. for 0.64 in.) MNL-116-99). Chicago, IL: PCI. every 24 in. (about the width of the 1. Calculate the required slope of the 2. PCI. 2014. PCI Bridge Design bottom flange). My recommendation is support to produce a tilt to counteract Manual. 3rd ed. 2nd release. (PCI to measure the angle against the web the measured sweep. For the BT-72 MNL 133-14). Chicago, IL: PCI. of the girder using a 2- or 4-ft level. girder, the uniform load (amount of 3. AASHTO (American Association of 2. Monitor the sweep regularly during lateral self-weight) w to cause a State Highway and Transportation y storage to ensure that sweep midspan deflection equal to the 0.64 Officials). 2017. AASHTO LRFD is sufficiently reduced before in. sweep is: Bridge Design Specifications. 8th ed. transportation. 384E I Washington, DC: AASHTO. w = ci yy f sweep 4. PCI. 2016. Recommended Practice y 4 () Conclusion 5L of Lateral Stability of Precast, 4 In most bridge girders, sweep, if it exists, 384( 4821 ksi) 37,543 in. Prestressed Concrete Bridge = ( ) 0.64 in. is likely to remain small and unnoticed. 3 () 4 ⎛ in. ⎞ Girders (PCI CB-02-16-E). Chicago, 5 130.5 ft ⎜1728 ⎟ However, as longer and lighter bridge () 3 IL: PCI. ⎝ ft ⎠ girders are fabricated, sweep may become ______= 0.0178 kip/ft more noticeable. This article provides an example for one cause of sweep in a The slope of the supports required to Dr. Bruce W. Russell is an associate professor girder, discusses increase in sweep that can straighten the 130.5-ft-long BT-72 at Oklahoma State University in Stillwater. occur at early ages when the girder is most

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ASPIRE Spring 2019 | 41 SAFETY AND SERVICEABILITY Managing Structures Affected by Delayed Ettringite Formation and Alkali-Silica Reaction

by Dr. David Rothstein, DRP, a Twining Company

elayed ettringite formation (DEF) tensioning) forces can influence cracking petrographer will see microcracks filled Dand alkali-silica reaction (ASR) are patterns, making them more linear with gel or ettringite that coalesce and durability mechanisms that can lead and aligned. The concrete should be feed into macroscopic cracks. to cracking that reduces the service life sampled for petrographic examination, of concrete structures. An overview and the samples should represent a suite Petrographers can categorize the severity of these mechanisms was provided in of different conditions ranging from of ASR qualitatively or quantitatively. the Summer 2018 issue of ASPIRE®. cracked to intact. Other samples may In qualitative rankings, severe ASR This article will discuss how to manage be collected to test compressive strength, is indicated by clear evidence of structures with ASR and DEF, with an splitting tensile strength, and other macroscopic cracking; moderate ASR by emphasis on ASR because it is far more engineering properties that may be of the presence of associated microcracks; common than DEF. interest for evaluating performance. and minor ASR by the presence of gel without cracks or microcracks. Investigating Damage Petrographic Investigations Quantitative methods include the The first step in managing ASR or DEF When damage is observed in the field, Damage Rating Index (DRI), which is to identify whether a structure has petrographic examination is used to assigns numerical “scores” to indicate been damaged. Investigations are done determine whether there is evidence the degree of damage.2 There is no visually on site, using petrographic of internal expansion. An experienced standardized threshold score to indicate techniques, and with other laboratory petrographer can determine if internal a particular level of damage, but the methods. expansion from ASR is occurring and DRI can nevertheless be a useful tool whether it is linked to macroscopic to compare different parts of a structure Field Investigations cracking. In many structures, cracks or assess the same parts of a structure at The starting point for all investigations observed in the field are from early-age different times. is on-site visual inspection of the mechanisms such as drying shrinkage structure and documentation rather than ASR. Early-age cracks tend Other Laboratory Investigations of deterioration such as cracks, to cut orthogonally to exposed surfaces Determining the chemical composition deformations, displacements, joint and to cut around aggregate particles. of the gel may help investigators deterioration, pop-outs, efflorescence, They also lack secondary deposits. understand whether the ASR is at an and discoloration of surfaces.1 In contrast, cracks caused by DEF early or late stage.3 Other laboratory tests Although map or pattern cracking is a or ASR contain significant deposits can help determine the likelihood that classic indicator of internal expansion, of ettringite or ASR gel, respectively. ASR will cause continued expansion. For the presence of reinforcement and When internal expansion progresses example, residual expansion tests can be prestressing (pretensioning or post- to the point of visible cracking, a used to monitor cores for length change

Photograph of map cracking on concrete Ultraviolet light photograph of polished slab from a concrete core affected by alkali-silica reaction. pavement affected by alkali-silica reaction. All The core was impregnated with a fluorescent epoxy. The yellow-green areas are filled with the epoxy. Photos and Figures: Dr. David Rothstein. The white arrows indicate examples of cracks.

42 | ASPIRE Spring 2019 Summary diagram of Damage Rating Index (DRI) results, showing how the method documents variations in the amount of damage. The bar chart summarizes the amount of distress associated with different indicators of distress associated with alkali-silica reaction (ASR). An entire bar represents a total DRI score, with higher numbers indicating more damage. The different colors within a bar indicate the different forms of damage that contribute to the total score. F11-2 and G12-4 show extensive damage, primarily associated with cracks with gel in the paste, and H11-3 shows essentially no damage. Abbreviations are as follows: CA, coarse aggregate; FA, fine aggregate; Frx, fracture; Rxn, reaction. under controlled conditions.4 Measuring of lithium-based compounds have been Application and Demonstration the water-soluble alkali content of the used with mixed results to arrest the Projects Volume I: Summary of concrete can show whether alkali in progression of ASR. A major concern Findings and Recommendations. the system is sufficient to sustain ASR. with such materials is the depth of Federal Highway Administration Remember that in cases where concrete penetration, which may be negligible in HIF-14-0002. https://www.fhwa. is exposed to deicing salts, the alkali some cases. dot.gov/pavement/pub_details. content of the concrete can increase over cfm?id=925. time because of the ingress of the salts.5 Other measures to prolong the 2. Sanchez, L.F.M., B. Fournier, M. serviceability of structures affected by Jolin, M.A.B. Bedoya, J. Bastien, Managing the Structure ASR may include structural repairs and J. Duchesne. 2016. “Use of Once ASR is identified as a concern, such as external post-tensioning, use of Damage Rating Index to Quantify the appropriate approach to manage carbon- or glass-fiber wraps, or other Alkali-Silica Reaction Damage it depends on the severity of the ASR methods to provide physical restraint. in Concrete: Fine Versus Coarse and the potential for future expansion. In cases where there is significant Aggregate.” ACI Materials Journal The first option is to simply monitor damage, cutting expansion joints or 113: 395–407. the structure by conducting field removing areas around damaged joints 3. Katayama, T. 1998. “Petrographic inspections at regular intervals. Crack may reduce stress. However, such Diagnosis of Alkali-Aggregate index maps and strain gauges can be measures are only temporary, and they Reaction in Concrete Based on used to determine if cracks are growing. do not mitigate future expansion. Quantitative EPMA Analysis.” Also, additional cores can be extracted Proceedings of the 4th International to be examined petrographically (DRI Conclusion Conference on Recent Advances in works well for this) and compared to The diagnosis of ASR or DEF in a Concrete Technology, Tokushima, cores evaluated previously. structure does not necessarily mean that Japan. immediate removal, replacement, or 4. Merz, C., and A. Leeman. 2013. If remediation is needed, several even repair is required. It is essential to “Assessment of the Residual approaches are available. The most conduct careful field and petrographic Expansion Potential of Concrete viable strategy for slowing or stopping investigations of the structure to obtain from Structures Damaged by the progression of ASR is to cut off the an understanding of the severity of the AAR.” Cement and Concrete water that feeds it. Studies have shown problem. In most cases, it is prudent Research 52: 182–189. that an internal relative humidity (RH) to implement field-based programs 5. Katayama, T. 2004. “Alkali- of 80% to 85% is essential to sustain to monitor and evaluate the behavior Aggregate Reaction Under the ASR in concrete.6 Often, the first step of the structure over time. Preventing Influence of Deicing Salts in the in keeping concrete elements below the ingress of water remains the most Hokuriku District, Japan.” Materials this RH threshold involves repairing or effective method to mitigate ASR in Characterization 53: 105–122. modifying drainage systems to redirect structures. In cases where damage is 6. Farny, J.A., and Kerkhoff, B. water flows away from and out of significant, structural repairs may be 2007. Diagnosis and Control structures. Waterproofing membranes, necessary. In all cases, experienced of Alkali-Aggregate Reactions in filling cracks and construction joints engineers, petrographers, and Concrete. PCA R&D Serial No. with appropriate materials, and contractors should be engaged to ensure 2071b. https://www.cement.org/ applying sealers or other surface that the proper strategies and methods docs/default-source/fc_concrete_ treatments may be adequate. Coatings for this work are deployed. technology/is413-diagnosis- that permit water vapor to escape are and-control-of-alkali-aggregate- preferred because they will facilitate the References reactions-in-concrete.pdf. drying of the structure. In some cases, 1. Thomas, M.D.A., K.J. Folliard, ______sealers that do not allow the structure B. Fournier, P. Rivard, and T. to breathe can make ASR worse because Drimalis. 2013. Methods for Dr. David Rothstein is the president and they trap moisture entering from Evaluating and Treating ASR- principal petrographer of DRP, a Twining untreated surfaces. Topical applications Affected Structures: Results of Field Company, in Boulder, Colo.

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44 | ASPIRE Spring 2019 FHWA

Advancing Bridge Repair and Preservation Using Ultra-High-Performance Concrete by Dr. Zachary B. Haber and Dr. Benjamin A. Graybeal, Federal Highway Administration

Ultra-high-performance concrete (UHPC) States, nearly 200 bridges in 27 states and the repaired or rehabilitated using UHPC-class is an advanced, fiber-reinforced, cementitious District of Columbia have been constructed us- materials, and, for the most part, each appli- composite material that has gained significant ing UHPC materials, and 93% of these projects cation has had unique aspects. (Refer to the attention from bridge owners and designers used UHPC for PBE connections. FHWA Interactive UHPC Bridge Map for ad- because of its excellent mechanical and dura- ditional details.2) bility properties. The rapid growth in UHPC’s Moving Beyond Four of these projects (in Colorado, Califor- popularity in the U.S. bridge market has been PBE Connections nia, Florida, and Rhode Island) marked the first spurred in part by its ability to provide a much- As UHPC-class materials become more prev- use of UHPC on state-owned highway bridges. needed, robust solution for closure pours in alent, new and innovative applications for these Each of these projects used relatively small vol- prefabricated bridge element (PBE) connec- materials in bridge design and construction will umes of UHPC material and were viewed as tions.1 This application has also been a com- continue to emerge. One emerging application relatively low risk by the bridge owners. As such, mon entry point for owners interested in the for UHPC in the U.S. highway bridge sector repair applications are becoming an alternative opportunities UHPC provides for bridge de- is for bridge repair, retrofit, and rehabilitation. entry point for bridge owners looking to gener- sign and construction. To date, in the United Since 2016, at least 10 U.S. bridges have been ate institutional knowledge and familiarize local

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A simple log-in to the PCI website is all that is needed to download these free resources. PCI Bridge Design Manual 3rd Edition, Second Release, August 2014 This up-to-date reference complies with the fifth edition of the AASHTO LRFD Bridge Design Specifications through the 2011 interim revisions and is a must-have for everyone who contributes to the transportation industry. This edition includes a new chapter on sustainability and a completely rewritten chapter on bearings that explains the new method B simplified approach. Eleven LRFD up-to-date examples illustrate the various new alternative code provisions, including prestress losses, shear design, and transformed sections. www.pci.org/MNL-133-11

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The PCI State-of-the-Art Report on State-of-the-Art Report on Full-Depth Precast Concrete Bridge Deck Panels Full-Depth Precast Concrete Bridge Deck Panels

Prepared by the PCI Committee on Bridges and the PCI Bridge Producers The PCI State-of-the-Art Report on Full-Depth Precast Concrete Bridge Deck Panels (SOA- Committee Under the direction of the Sub-committee for the State-Of-The-Art Report on Full-Depth Precast Concrete Bridge Deck Panels 01-1911) is a report and guide for selecting, designing, detailing, and constructing precast Ultra-high-performance concrete repair of connections U.S. Department of Transportation Federal Highway Co-sponsored by: Administration concrete full-depth deck panels for bridge construction. This report is relevant for new bridge between precast, prestressed concrete voided-slab beams in First Edition construction or bridge-deck replacement. Florida. Photo: Florida Department of Transportation. www.pci.org/SOA-01-1911

eBooks are fully searchable with hot links to references, enabling direct access to the internet. ASPIRE Spring 2019 | 45 The first installation in the United States of an ultra-high- Ultra-high-performance concrete was used for the repair of a performance concrete bridge deck overlay was in Iowa. Photo: midspan spliced U-girder closure pour. Photo: SEMA Construction Federal Highway Administration. Inc. contractors with UHPC. Repair of Existing Connections Moving Forward The following innovative UHPC-based repair UHPC-class materials are known to be excel- The advancement of bridge repair and preser- solutions have been implemented, conceptual- lent candidates for closure pours for PBE con- vation practices using innovative materials such ized, or laboratory tested: nections because these materials can provide as UHPC is a current area of focus for research • UHPC overlays for bridge deck rehabilitation durable connections and very compact rein- within the Structural Concrete Research Group • Repair of existing connections between PBEs forcement details.1 The Florida Department of at FHWA TFHRC. We are striving to develop • Structural patching of reinforced concrete Transportation (FDOT) leveraged these charac- new solutions to solve some of the continual bridge decks, prestressed concrete girders, teristics to repair an existing bridge (constructed challenges related to bridge preservation. We and bearing pedestals in 1978) with precast, prestressed concrete hope this article spurs innovative thinking as it • Expansion joint repair with UHPC headers voided-slab beams. The units were transversely relates to concrete bridge repair, and we look for- or replacement using UHPC link slabs post-tensioned and employed partial-depth, ward to assisting owners with the identification, • Seismic retrofit of deficient bridge column- conventionally grouted shear keys. After years of design, and installation of innovative solutions. footing lap splices service, reflective cracking became apparent in • Structural strengthening of deteriorated the bridge’s asphalt overlay, and there was evi- References girder ends dence of differential deflection between adjacent 1. Graybeal, B.A. 2014. Design and Construc- The first three of these applications are summa- slab units. Instead of replacing the superstruc- tion of Field-Cast UHPC Connections. Fed- rized here. ture, FDOT decided to remove the existing con- eral Highway Administration (FHWA) nection regions using hydrodemolition, install FHWA-HRT-14-084. https://www.fhwa.dot UHPC Overlays for Bridge Decks additional reinforcement, and replace the re- .gov/publications/research/infrastructure/ In one of most promising UHPC-based moved concrete with UHPC. Laboratory testing structures/14084/14084.pdf. bridge repair applications, UHPC is used as of similar connections using UHPC between ad- 2. FHWA. 2018. Ultra-High Performance Con- a thin, bonded overlay for bridge deck reha- jacent box beams has demonstrated that UHPC crete Interactive Web Map. http://usdot.maps. bilitation. As an overlay, UHPC can provide has the ability to create full composite action and arcgis.com/apps/webappviewer/index.html? structural strengthening, protection from chlo- robust performance.6 id=41929767ce164eba934d70883d775582. ride and water ingress, and good resistance 3. Haber, Z.B., J.F. Munoz, I. De La Varga, to mechanical abrasion, which reduces the Structural Patching and and B.A. Graybeal. 2018. Ultra-High Per- tendency for rutting. This deck rehabilitation Localized Repairs formance Concrete for Bridge Deck Over- can be achieved with a 1- to 3-in.-thick layer UHPC-class materials have been used for lays. FHWA-HRT-17-097. https://www. of UHPC, which minimizes material volume localized repair of expansion joint headers, fhwa.dot.gov/publications/research/ and additional dead load. This repair method, structural patching of bridge decks, and struc- infrastructure/bridge/17097/17097.pdf. which was pioneered in Europe, and has been tural patching of prestressed concrete bridge 4. Haber, Z.B., J.F. Munoz, and B.A. Gray- deployed on more than 20 European bridges, girders. An example of structural patching beal. 2017. Field Testing of an Ultra-High is particularly competitive when an owner is was performed on a recently constructed, Performance Concrete Overlay. FHWA- looking to extend the life of a structure that is multispan interstate flyover. This bridge had HRT-17-096. https://www.fhwa.dot.gov/ otherwise difficult to replace, such as a life-line a spliced U-girder superstructure. During con- publications/research/infrastructure/ structure, a historically significant bridge, or a struction, poorly consolidated concrete was structures/bridge/17096/17096.pdf. structure in a challenging geographic or urban identified within a closure pour at a midspan 5. Graybeal, B.A. 2017. Adjacent Box Beam area. To date, there have been three UHPC girder-to-girder splice location. The poorly Connections: Performance and Optimization. overlays installed in the United States. The consolidated concrete was removed and re- FHWA-HRT-17-094. https://www.fhwa. first of these installations was on a reinforced placed with UHPC. UHPC was selected as the dot.gov/publications/research/ concrete slab bridge in an agricultural region in repair material because it bonds very well with infrastructure/structures/bridge/ Iowa.3,4 UHPC overlays are an active research steel reinforcement and existing concrete, and 17094/17094.pdf. topic at the Federal Highway Administration because it is highly flowable and self-consoli- 6. Graybeal, B.A. 2011. Ultra-High Perfor- (FHWA) Turner-Fairbank Highway Research dating. The region to be repaired was highly mance Concrete. FHWA-HRT-11-038. Center (TFHRC), and additional information congested; thus, the repair material needed to https://www.fhwa.dot.gov/publications/ can be found in references 3 through 6. have excellent flow properties. research/infrastructure/structures/ 11038/11038.pdf.

46 | ASPIRE Spring 2019 STATE Alabama

by William (Tim) Colquett, Alabama Department of Transportation

oncrete has been a mainstay of Constructability, schedule, and aesthetics CAlabama’s highway bridge infrastructure were among the reasons that this approach for many years. There are concrete- was chosen. The segmental girders provide superstructure standard drawings that date longer span lengths, eliminating substructure to the 1920s, and some of the bridges built and providing more space beneath, which from those drawings are still in service. With city officials intend to use for public events. advances in technologies, materials, and Also, noise levels, both above and below, construction techniques, bridges that would will be reduced because concrete provides have traditionally been constructed of steel much-improved noise abatement under the are now designed using concrete. bridges and because longer span lengths and Alabama’s bridge inventory consists of continuity will eliminate joints, reducing 15,980 bridge structures, including 5757 noise from wheel strikes. bridges and culverts that are owned and The segments are being cast off site and maintained by the State. Approximately stockpiled until a section of the bridge is Precast concrete caps were set onto precast concrete 69% of those structures (excluding culverts) closed, at which time the contractor will columns for the Interstate 59/20 Central Business have concrete superstructures. Concrete set the segments. Prior to closure, while District Bridge project. Photo: ALDOT. construction has proved to be efficient, the existing bridges are still in place, economical, and aesthetically pleasing. foundation work is being completed using low-overhead equipment that can operate Concrete in the confined space. Because of the area’s karst geology, construction has subsurface conditions vary within small distances; therefore, foundations include proved to be efficient, micropiles, driven-steel piling, and drilled shafts. Micropiles are being used for the economical, and first time in a widespread application on a bridge project in Alabama. Precast concrete aesthetically pleasing. columns and caps are further expediting construction, with grouted splice sleeves A segment for the Interstate 59/20 Central Business These benefits are nowhere more being used for connections between precast District Bridge project is removed from the casting apparent than with the current Interstate concrete elements and the footings. bed. Photo: ALDOT. 59/20 Central Business District bridge The contractor has 14 months (from replacement project currently underway in January 2019 to spring 2020) to complete downtown Birmingham, Ala. The largest and open the new bridge system. It will be contract ever let by Alabama Department of erected using the span-by-span method Transportation (ALDOT), the $475 million with ground-based shoring. An aesthetics project replaces 6600 ft of steel girders and package includes Wi-Fi-controlled several fracture-critical steel bent caps for multicolored lighting installed beneath the structures that run through the downtown bridge that can be programmed for events at area. The circa-1971 bridges were designed the bridge. To further expedite construction, for average daily traffic (ADT) of 80,000; electrical infrastructure was preinstalled in however, ADT is projected to reach 225,000 the segments. in 2035. The old bridges lack shoulders and have obsolete geometry, with some entrance Use of Accelerated Bridge and exit ramps placed on the left. Construction Techniques Micropiles were used in some locations of the The new bridges, which have wider Accelerated bridge construction (ABC) Interstate 59/20 Central Business District Bridge cross sections to accommodate additional techniques have been in use in Alabama project because of the varying soil conditions in the lanes and full shoulders, eliminate for many years. In some ways, the state area. This was the first use of micropiles in the state. some of the entrance and exit ramps and was advancing ABC methods before ABC Photo: ALDOT. utilize segmental concrete box girders. became an industry buzzword. For example,

ASPIRE Spring 2019 | 47 STATE

Construction of one of the new twin bridges on the Ross Clark Circle (U.S. Route 231) over Beaver Creek culvert in Dothan, Ala. The rollers and steel tracks shown in the photo on the right were used with hydraulic jacks to slide the new bridge into place. Photos: ALDOT. short-span precast concrete bridges and quickly as possible to minimize traffic These designs usually provide the best substructures have been a common feature disruptions in an area with high ADT. economy, aesthetics, durability, and speed of of Alabama’s off-system roadways for years. In lieu of constructing a new culvert, construction for the state. ALDOT’s solution was to retain the existing In some ways, the culvert, partially remove the fill from the Emerging Delivery and culvert’s top, and span over it with parallel Design Methods state was advancing 120-ft-long bulb-tee girder spans, 54 ft and Design options for bridges may expand as 63 ft wide, each supported by steel piles and ALDOT ventures into new delivery methods. ABC methods before cast-in-place concrete abutments. For example, for the Interstate 10 (I-10) The contractor constructed the Mobile River Bridge, a planned six-lane ABC became an industry abutments beneath live traffic by using structure that will be the state’s second steel trench boxes with removable lids that cable-stayed bridge, three prequalified buzzword. accommodated traffic during peak hours teams now are putting together design, Perhaps the most prominent use and then could be removed in off-peak cost, and schedule proposals for the project, of ABC on state highways came in 2002 times to allow piles to be driven. Once the which is being financed through a public- and 2004, when two different structures piles were driven, the lids were put back private partnership. This approach offers in the Interstate 59/20 interchange were in place while workers beneath completed the only way that the state can afford the damaged beyond repair after tractor construction of the abutment caps. project, which will cost between $800 trailers wrecked under the bridges and The superstructure was constructed on million and $1 billion. their fuel loads were ignited. These bridges, roller bearings, so it could be rolled into located in what is sometimes called the place during specific windows of closure Design options “Malfunction Junction” due to the heavy times. When the slide was ready, traffic was traffic and diverging-diamond geometry, shut down, the trench boxes were removed, for bridges may expand had to be replaced as rapidly as possible to and the spans were rolled into place. minimize travel disruptions on an already The first bridge was rolled into place and as ALDOT ventures into difficult route. Steel spans were replaced completed in three days, while the second with prestressed concrete bulb-tee girders was completed in two. new delivery methods. on an accelerated schedule. One span was Successfully completing this project replaced in 36 days, and the other was back required ALDOT to take a proactive The I-10 Mobile River Bridge will also be in service in 38 days. Prefabrication of span approach with the contractor. This close the state’s first design-build project, which components while the site was prepared was relationship allowed dialogue and became possible when legislation was passed a key to that speed. ALDOT has incorporated suggestions to flow easily, facilitating the to allow the use of that delivery method on similar techniques into other projects to quick processing of issues and creating a projects costing more than $100 million. help reduce user costs and keep traffic pattern that can be used on future projects Clearly, many new concepts will emerge moving smoothly. where such ABC techniques may be from this process, and ALDOT is watching Recently, another ABC technique was appropriate. closely to determine what benefits these successfully deployed for the bridge slide Although these projects demonstrate approaches can provide for future projects. in the $2.43 million culvert replacement ALDOT’s willingness to use new techniques on Ross Clark Circle (U.S. Route 231) in when needed, Alabama’s bridge projects Bridge Aesthetics Dothan, Ala. (see the article on this project typically use conventional construction New design ideas will also aid in creating in the Fall 2016 issue of ASPIRE®). The methods. Most bridges are built with more aesthetically pleasing bridges, which objective was to widen the structure from traditional concrete designs, typically has become a higher priority. The range of two to three lanes in each direction as using AASHTO-type and bulb-tee girders. aesthetic options available with concrete has

48 | ASPIRE Spring 2019 broadened, with new decorative methods being produced and material costs declining. Decorative railings, abutments, and even lighting systems, such as the one for the Birmingham Central Business District project, are becoming more prominent. A recent project emphasizing aesthetics is the replacement of the Moores Mill Road Bridge in Auburn, which spans the busy Interstate 85 corridor between Atlanta, Ga., and Montgomery, Ala. Faced with growing ADT, Auburn wanted a wider bridge, with a dedicated sidewalk and aesthetic treatments that suited the structure’s high- visibility location. The new design features two 120-ft-long spans using 54-in.-deep modified prestressed concrete bulb-tee girders, a 74-ft-wide deck between gutters, and a 9-ft-wide sidewalk. Precast concrete Formliners were used to simulate brick on the Moores Mill Road Bridge over Interstate 85 in Auburn, Ala. The pier columns expedited the work in the I-85 “brick” was then stained to resemble the brick used for buildings at nearby Auburn University. Photo: ALDOT. median. Formliners were used to simulate brick on the barrier rails, portions of the square prestressed concrete piles with cast- built in Huntsville, Ala. columns, abutment wings, and toe wall. in-place concrete caps and deck. Also, owing to the varied and complex They were stained to closely resemble Decorative reliefs were cast into the soil conditions in Alabama, micropiles the brick color used at nearby Auburn outside fascia of the girders, and a varied are expected to be used more often in the University. Decorative lighting and railing height, custom aluminum “wave” shape future. They offer a good alternative when were installed to complement the simulated was designed for the railing to complement soil conditions create challenges and the brick. The $3.79 million bridge opened in the beach environment. The $1.71 million Birmingham Central Business District the spring of 2018. bridge opened in 2015. project has demonstrated their advantages. Even along Alabama’s coast, where Alabama’s future may include more durability is the primary consideration, Looking to the Future design-build and public-private partnership aesthetic design is a growing priority. More construction options will be projects, as those delivery methods The recent bridge replacement on State added to the toolbox as the state adjusts to potentially provide benefits and more Route 182 in Gulf Shores, Ala., shows how advanced techniques. For example, ALDOT innovative designs in some situations. durability and aesthetic details can be will soon let its first project using Northeast Traditional approaches often offer the best combined. The new bridge is a 191-ft-long, Extreme Tee (NEXT) beams. They are a solution, but the state is open to new options three-span continuous structure that uses good solution for specific applications, and that will help create economical, efficient, precast concrete arch girders with just mild ALDOT expects to use them on other future and aesthetically pleasing designs. reinforcement (no prestressing or post- projects as well. Florida I-beams (FIBs) ______tensioning). The bents are composed of are another option, with good potential spun precast concrete cylinder piles and for specific applications. ALDOT is closely William (Tim) Colquett is state bridge precast concrete caps, which were chosen watching the use of 100-ft-long FIB36 engineer with the Alabama Department for their durability. The abutments feature beams for a privately funded bridge to be of Transportation in Montgomery.

To reflect the maritime location, decorative elements including dolphin The top priority for the new State Route 182 Bridge over the channel at Little Lagoon in shapes, were cast into the fascia and a custom aluminum “wave” shape for Gulf Shores, Ala., was durability, but designers also added aesthetic touches to play off the the railing was added to the State Route 182 Bridge over the channel at structure’s oceanside setting. Photo: Scott Bridge Company. Little Lagoon in Gulf Shores, Ala. Photo: ALDOT.

ASPIRE Spring 2019 | 49 PCI Offers New Transportation eLearning Modules Courses on Design and Fabrication of Precast, Prestressed Concrete Bridge Beams The PCI eLearning Center is offering a new set of courses that will help experienced bridge designers become more proficient with advanced design methods for precast, prestressed concrete flexural members. There is no cost to enroll in and complete any of these new bridge courses. The courses are based on the content of AASHTO LRFD and PCI publications. These include several State-of-the-Art and Recommended Practice publications, as well as the PCI Bridge Design Manual. These are available for free to course participants after registering with a valid email. While the courses are designed for an engineer with five or more years of experience, a less experienced engineer will find the content very helpful for understanding concepts and methodologies. Where applicable, the material is presented as part of a “real world” example of a complete superstructure design so that students can see how actual calculations are completed according to the AASHTO LRFD specifications. All courses on the PCI eLearning Center are completely FREE. Go to: http://elearning.pci.org/ PCI eLearning Precast, Prestressed Concrete Bridge Girder Series

Preliminary Precast, Prestressed Concrete Design (T110) Prestressed Losses (T135)* Materials and Manufacturing of Precast, Prestressed Shear (T145)* Concrete (T115) End Zone Design (T160) Design Loads and Load Distribution (T120) Extending Spans (T310)* Flexure Service (T125)* Bearing Pads (T450)* Flexure Strength (T130) In-Service Analysis Load Rating (T710)* Full-Depth Precast Concrete Deck Panels Series

Introduction on Full-Depth Panel Precast Concrete Deck Production and Construction Details of Full-Depth Precast System and Its Advantages (T210) Concrete Deck Panels (T220) Design and Detailing of Full-Depth Precast Concrete Deck Case Studies and Emerging Developments of Full-Depth Panels (T215) Precast Concrete Deck Panels (T225) Lateral Stability of Precast, Prestressed Concrete Bridge Girders Series

Introductory Material and Hanging Girders (T520)* Seated Girders and Stability Issues from Bed to Bridge (T525)* Stability of Transported Girders (T523)* Stability Calculations and Sensitivity Analysis (T527)* *These PCI eLearning Courses will be available soon. This material is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange under DTFH61-13-D-00010 Task No. 5010. The U.S. Government assumes no liability for the use of the information. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this material only because they are considered essential to the objective of the material. They are included for informational purposes only and are not intended to reflect a preference, approval, or endorsement of any one product or entity. AASHTO LRFD AASHTO LRFD Bridge Design Specifications: Service IV Load Combination

by Dr. Oguzhan Bayrak, University of Texas at Austin

ur ASPIRE® team recently received components create “working” or were based on judgment, considering Oa question about when and why allowable stress conditions that must be uncertainty and variability of the loads we use the provision for prestressed kept below a certain fraction of actual and section properties. (pretensioned and post-tensioned material strength. concrete) substructure solutions with The transition to load and resistance the load combination for the Service After nearly half a century of factor design (LRFD) for concrete simply IV limit state, which is one of many successful use, ASD was set aside, and involved the formal calibration of the limit states in the American Association a new direction was taken based on the load and resistance factors used in LFD of State Highway and Transportation more rigorous notion of the factor of design by using statistical methods and Officials’ AASHTO LRFD Bridge Design safety against failure of the section. This field data on loads, material properties, Specifications.1 This article aims to shed was intended to give a more uniform and other aspects. Subsequently, light on that topic. factor of safety against failure, which variability in material resistances, the was not possible with ASD. accuracy with which structural capacities Before we address the Service IV load can be estimated, and the consequences combination specifically, let us first For load factor design (LFD), the of different modes of failure were all consider the historical development strength (resistance) of the section was brought into the LRFD design process. of bridge design specifications. From compared to service loads that were the issuance of the first bridge design individually increased by load factors The first edition of the AASHTO specifications in the late 1920s until that were greater than 1.0. Prior to the LRFD specifications was published early 1970s, bridges were designed by comparison of strength to demand of in 1994. Since 1994, the AASHTO using allowable stress design (ASD) the applied loading, the resistance was LRFD specifications have been revised principles. In a nutshell, ASD is based reduced by a resistance factor that was or updated as our knowledge about the on the premise that stresses created typically less than 1.0. The magnitudes performance of concrete bridges has by loads acting on bridges and their of the load and resistance factors evolved. Our decisions while developing new techniques, revising older methods, Load combinations and load factors from Table 3.4.1-1 in the AASHTO LRFD and calibrating load and resistance specifications. Figure: AASHTO LRFD Bridge Design Specifications, 8th edition. factors have been informed by data generated in new experimental programs, the advent of increased computing power, the associated development of advanced analysis techniques, and the field performance of concrete bridges.

In the eighth edition of the AASHTO LRFD specifications, which was published in 2017, loads and load combinations are covered in Section 3.1 As stated in that section, we have five strength limit states, two extreme event limit states, and four service limit states, in addition to the two fatigue and fracture limit states. The Service IV limit state relates to controlling tension in prestressed concrete columns, with the ultimate goal of preventing or minimizing the chances of cracking in these substructure elements to improve durability and maintain a higher flexural stiffness.

ASPIRE Spring 2019 | 51 The use of segmentally constructed years. The current AASHTO LRFD columns and precast, prestressed concrete specifications are based on 3-second columns is currently proliferating as gust wind speed, which means that the project stakeholders aim to accelerate wind speed is averaged over 3 seconds. bridge construction and leverage the greater quality control associated with The use of a large number of loads plant-fabricated concrete elements. Also, and load combinations is commonly post-tensioned cantilever and straddle facilitated by design software. Using caps are growing in use as we renew the computers for the analysis and design interstate system. These substructure unquestionably gives us a chance elements should be designed for many to improve the precision and levels of load combinations, including the reliability in our structural designs to a Service IV load combination. In some degree we could not have dreamed of Service IV load combination was used to cases, the load combination of Service during the major infrastructure expansion design the precast concrete segmental IV may control the design of these in the United States after the conclusion substructures for the U.S. Route 183 substructure elements. The commentary of World War II. Establishing uniform elevated viaduct in Austin, Tex. Photo: Dr. for Article 3.4.1 of the AASHTO LRFD levels of safety has many design and Oguzhan Bayrak. specifications explains the evolution of cost benefits and reduces environmental transportation, erection, construction, the Service IV load combinations. impact by removing unnecessary and service is an important goal of design conservatism (that is, overdesign) where as we aspire to see our concrete bridges To better understand the historical appropriate. With these important serve our communities for at least 100 evolution of the Service IV load goals stated, we must remain alert in years. combinations, we must appreciate our designs to ensure that all important the fact that previous editions of the or controlling load applications are Reference AASHTO LRFD specifications were considered. Limiting tensile stresses in based on fastest-mile wind speed. In prestressed concrete (both cast-in-place 1. American Association of State Highway other words, the wind effects were and precast) substructure elements and Transportation Officials (AASHTO). averaged over different lengths of time (piles, caps, footings, and columns that 2017. AASHTO LRFD Bridge Design over a distance. This approach has are pretensioned or post-tensioned) Specifications, 8th ed. Washington, DC: been revised and modernized over the while in a fabrication plant and during AASHTO.

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52 | ASPIRE Spring 2019

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